PRELIMS Flashcards
1
Q
The machine on which sections are cut
A
Microtome
2
Q
Essential parts of a Microtome
A
1. Knife carrier and Knife
2. Block holder
3. Ratchet feed wheel, pawl, and adjustment screws
3
Q
Types of Microtome
A
1. Rocking Microtome
2. Rotary (Minot) Microtome
3. Freezing Microtome
4. Ultra-thin Microtome
5. Sliding or Base Sledge Microtome
4
Q
The histology technician’s tool of his profession and becomes a personal possession.
A
Microtome Knife
5
Q
Each technician should be given at least __ good knife/knives.
A
2
6
Q
It is where the tissue is held in position.
A
Block holder
7
Q
Adams developed this in 1789.
A
Sliding or Base Sledge Microtome
8
Q
Used for actual cutting of tissue sections
A
Knife carrier and knife
9
Q
Caldwell Trefall invented this in 1881.
A
Rocking Microtome
10
Q
Used to line up the tissue block in proper position with the knife, adjust the proper thickness of the tissue for successive sections
A
Ratchet feed wheel, pawl and adjustment screws
11
Q
Principle of the Microtome
A
A pawl is brought into contact with a ratchet wheel, which is connected to a mill head micrometer screw. This action turns the ratchet wheel, which in turn rotates the screw. By this means the block is moved towards the knife at a predetermined thickness.
12
Q
It consists of central screw by which the block holder is perforated, attached to it is the food pipe carrying carbon dioxide from a cylinder. A simple lever - operated valve allows the release of rapid intermittent burst of carbon dioxide that freezes the block and the tissue.
A
Freezing Microtome
13
Q
T or F: The knife is usually mounted below the block when using a freezing microtome.
A
Negative. The knife is usually mounted above the block.
14
Q
Minot invented this in 1885-1886.
A
Rotary (Minot) Microtome
15
Q
This is capable of cutting sections required for electron microscope.
A
Ultra-thin microtome
16
Q
Ultra-thin Microtome is capable of cutting sections at ____.
A
0.5 micron
17
Q
Queckett invented this in 1848.
A
Freezing microtome
18
Q
A relatively small length of knife is available to use; it is dangerously placed with blade up.
A
Rotary (Minot) Microtome
19
Q
Used in preparation for serial sections. Ribbons of 60-90 sections are obtained with ease.
A
Rocking microtome
20
Q
Recommended for cutting extremely hard blocks.
A
Sliding or Base Sledge Microtome
21
Q
It is not suitable for cutting large blocks as in the sliding microtome but is convenient for cutting serial sections making it faster for large number of routine blocks.
A
Rotary (Minot) Microtome
22
Q
It is the simplest of all microtomes, the tissue block being mounted on the end of a spring poised rocking arm, the knife is held in a horizontal position, the blade face up and slightly inclined towards the block.
A
Rocking microtome
23
Q
There are two types of this microtome.
A
Sliding or Base Sledge Microtome
24
Q
Its knife consist mainly of selected fragments of broken plate glass. Special diamond knife can be used.
A
Ultra-thin Microtome
25
Three basic shapes of the microtome knife
**1. Biconcave**
**2. Plane-concave**
**3. Plane Wedge**
26
Routinely used for frozen sections and extremely hard specimens embedded in paraffin wax. It is also used for paraffin blocks being cut on the rotary microtome
Plane Wedge
27
For paraffin sections with a rocking or rotary type of microtome. Can be used on a carbon dioxide freezing microtome
Biconcave
28
One slide of thin knife is flat and the other is concave. There are 2 degrees of concavity available. The one with the lesser concavity is used for celloidin sections. The more concave side is used for paraffin sections on the sledge, rotary or rocking microtome.
Plane-concave
29
Care of the microtome knives
1. Store the knife in its box when not in use
2. Never lay the knife flat in the bench
3. Never allow the edge to become badly "nicked". It is advisable to have a second knife for cutting bone and hard tissue
4. The edge of the knife should be "touch up" daily before use
5. Always use a back, when required for sharpening. This is not necessary with biconcave knives.
6. The knife should be cleaned with xylene or toluene before and after use. Never allow it to become rusty.
7. Never lend or borrow a knife.
30
Has a vibrating frosted glass plate along which the knife is pushed, edge first, held at the correct angle by a knife holder.
Automatic Knife Sharpener
31
After how many strokes is the blade of the automatic knife sharpener automatically turned over?
4 strokes
32
A cold chamber, which is kept at a temperature of -20°C. It is used to cut frozen tissue. It has replaced the carbon dioxide freezing microtome for frozen sections.
Cryostat
33
\_\_\_\_ of tissue can be cut using a cryostat
1-4 u
34
An automatic tissue processor that performs fixation, dehydration, clearing, and paraffin infiltration
Autotechnicon
35
Used for embedding tissue in an easier way.
Autotechnicon
36
Autotechnicon parts
1. **Carrier**
2. **Sample basket** - for the specimen
3. **Receptacle** - contains the reagents
4. **Delay timer** - it enables the operator to delay the beginning of the processing cycle for any desired time up to 60 hours
5. **Timing disc panel**- it contains the power switch, selector, pilot light, transparent plastic door with lock and key
6. **Tissue Embedding Center**
37
Essential parts of the Autotechnicon
**1. Freon Refrigeration System -** provides the instant cooling of the exchange plate
**2. Paraffin Melting Chamber- **forms a penthouse on the right-hand side of the unit and on the lower left of this chamber is a microswitch dispenser. This chamber maintains an optimal paraffin temperature with an adjustable thermostatic control.
**3. Microscreen **- filters particles or sediments
**4. Micro-switch Dispenser **-Porvides a non-clogging flow of molten paraffin for the casting of molds when the plate is gently pressed
**5. Hot and Cold Orientation Platforms **-For different operations of the embedding procedure.
**6. Waste Drawer -**Catches excess paraffin
**7. Hot Well - **To pre-heat forceps
38
Also known as the wax oven designed to store paraffin in its liquid state, maintaining a temperature of 2-5°C higher than the melting point of the wax
Paraffin oven
39
Designed primarily for use as a micro-sectioned tissue flotation bath.
Flotation water bath
40
Glass stoppered jars provided at the bottom pad with grooves, usually for fixation and staining.
Coplin jars
41
Methods in the most common usage for the preparation of specimens for examination
1. Sectioning
2. Smears
3. Dissociation
4. Vital Staining
5. Autoradiography
42
The most common method of preparing tissues for histologic examination
Sectioning
43
12 steps of histopathologic techniques
1. Numbering
2. Fixation
a. Decalcification- if tissue contains calcium (bone and teeth)
3. Dehydration
4. Clearing
5. Infiltration or Impregnation
6. Embedding, Casting or MOLDING
7. Blocking
8. Trimming
9. Sectioning or Cutting
10. Staining
11. Mounting
12. Labeling
44
Advantage of Sectioning
Cell can be studied in their relationship to one another in the tissue and not divorced from their natural background
45
In what method is the tissue subjected to the 12 steps of histopath techniques?
46
Can be made by either pressing the cut surface of tissue into slide, an impression smear, spreading material with a wire loop, brushing it between two slides or streaking the specimen into the slide. The preparationg is then fixed, stained, and mounted.
Smears
47
The tissue is teased with needles into a watchglass containing an indifferent medium such as normal saline and then transferred to a microscpe slide for examination.
Dissociation
48
Advantage/Disadvatge of Dissociation
A: Cells are examined while still alive.
D: Cells are divored from their normal surroundings.
49
Used to locate the presence and position of mineral elements in the tissue.
Microincineration
50
The cells maybe stained by dissociating tissue in a simple staining solution (supravital staining) a method often used to stain reticulocytes, or in the living organism by injecting a dye into the tissue (intravital staining)
Vital Staining
51
Radioactive isotopes are injected into organs which are then fixed and sectioned
Autoradiography
52
Type of Examination Requested
1. Routine Paraffin Method (most common)
2. Papanicolaou Staining method
3. Rush Frozen Section
4. Decalcification of Bones and Hard Tissues
53
Enumerate: Simple Fixatives
**I. Aldehyde Fixatives**
**II. Metallic Fixatives**
**III. Picric Acid fixatives**
**IV. Acetic Acid fixative**
**V. Acetone**
**VI. ALcohol Fixative**
**VII. Osmium Tetroxide fixative**
54
Enumerate: Aldehyde Fixatives
1. Formaldehyde
2. Glutaraldehyde
3. Paraformaldehyde
55
A gas produced by the oxidation of methyl alcohol and is soluble in water to the extent of 40% by weight. A powerful reducing agent and used as such in the make up for Helly's fluid.
Formaldehyde
56
Usual fixation time if formaldehyde is used.
12-24 hours
57
Often becomes turbid afer prolonged storage because of the formation of paraformaldehyde which is caused by the polarization of formaldehyde.
Commercial formaldehyde
58
Methods for removal of Formalin Pigments
**1. Kardasewitsch's Method**
**2. Lillie's Method**
**3. Picric Acid Method**
59
An aldehyde with a MW of 100 or 2 formaldehyde residues linked by a straight 2 Carbon chains
Glutaraldehyde
60
GLUTARALDEHYDE:
A ___ is best used for small fragments and small needle biopsises, fixed adequately for 2-4hrs in room temp. A _____ is recommended for large tissue not exceeding 4mm in thickness and for 12-24hrs at room temp.
2.5% solution; 4%
61
A polymer of formaldehyde and is a white powder. It is used in a 4% strength at 4°C.
Paraformaldehyde
62
Enumerate: Metallic Fixatives
A. Mercuric Chloride
B. Chromate Fixative
C. Lead Fixative
63
Frequently used in saturated solution. At room temp, its solubility in water is 7%.
Mercuric Chloride
64
Strong oxiding agents and should not combine with reducing agents such as alcohol and formalin. These are used in 1-2% aqueous solution.
Chromate Fixatives
65
Used in 4% aqueous solution
Lead Fixative
66
Usually used in strong or saturated solution. Its solubility is that 1.7g will dissolve in 100ml of distilled water at 15?°C
Picric Acid Fixatives
67
Chemically, picric acid is \_\_\_\_\_\_\_\_\_\_.
2,4,6-trinitrophenol
68
69
Used at ice-cold temperature (-40°C)
Acetic Acid Fixative
70
Used in ice-cold temp (40°C) and is used only in enzyme studies
Acetone
71
Used for rapid denaturing and precipitation of proteins by destroying hydrogen and other bonds. Must be used in concentration from 70-100% bec lesser concentrations lyse the cells
Alcohol Fixative
72
Commonly known as Osmic Acid.
Osmium Tetroxide Fixative
73
It is pale yellow. It dissolves in water (up to 6% at 20°C) forming a solution which is a strong oxidizing agent
Osmium Tetroxide Fixative
74
Enumerate: Compound Fixatives
I. Micro-anatomical Fixatives
II. Cytological Fixative
75
Enumerate: Micro-anatomical Fixatives
**A. 10% Formal-saline**
**B.10% Buffered Formalin**
**C. Heidenhain's Susa Solution**
**D. Formol Sublimate**
**E. Formol Saline Sublimate**
**F. Zenker's Solution**
**G. Zenker's Formol (Helly's Fluid)**
**H. Bouin's Solution**
76
Recommended for materials from the nervous sustem and general post mortem materials.
10% Formol-saline
77
Fixation time for 10% Formol-saline
12-24 hours
78
Recommended for preservation of post mortem surgical research specimens
10% Buffered Formalin
79
Fixation time of 10% Buffered Formalin
24 hours or more
80
Recommended for biopsies of the skin
Heidenhain's Susa Solution
81
Fixation time for Heidenhain's Susa Solution
3-12 hours
82
Recommended for routine post mortem materials
Formol Sublimate
83
Fixation time for Formol Sublimate
3-24 hours
84
Recommended for post mortem materials
Formal Saline Sublimate
85
Fixation time for Formal Saline Sublimate
3-24 hours
86
Recommended for post mortem materials 2.0
Zenker's Solution
87
T or F: Fixation time of Zenker's Solution if the same with Formol Saline Sublimate and Formol Sublimate.
Positive. All three - 3-24hours fixation time
88
Recommended for pituitary tissues and bone
Zenker's Formol (Helly's Fluid)
89
Fixation Time Zenker's Formol (Helly's Fluid)
12-24 hours
90
Recommended for embryos
Bouin's Solution
91
Enumerate: Nuclear Cytological Fixatives
A. Flemming's Fluid
B. Carnoy's Fluid
C. Bouin's Fluid
D. Newcomer's Fluid
92
Enumerate: Cytoplasmic Cytological Fixative
A. Flemming's Fluid
B. Champy's Fluid
C. Regaud's Fluid
D. Orth's Fluid
93
Recommended for nuclear structures
Flemming's Fluid
94
Fixation time for Flemming's fluid
24-48 hours
95
Recommended for chromosomes study, lymph nodes and urgent studies for glycogen
Carnoy's Fluid.
96
Fixation time for Carnoy's Fluid
1/2 to 3hours
97
Recommended for embryos and glycogen. Fixation time is 6-24 hours.
Bouin's Fluid
98
Recommended for mucopolysaccharides, nuclear protein and chromosomes. Fixation time is 2-3hours.
Newcomer's Fluid
99
Recommended for cytoplasmic structures. Fixation time 26-48 hours
Flemming's Fluid (minus acetic acid)
100
Recommended for mitochondria, Golgi elements and fats. Fixation time:24-48 hours
Champy's fluid
101
Recommended for mitochondria and yolk. Fix time is 12hours
Regaud's Fluid (Moller)
102
Recommended for study of early degenerative process and tissue necrosis. Fix time: 36-72 hours
Orth's Fluid
103
The process of removing extracellular and intracellular water from tissue following fixation and prior to wax infiltration
Dehydration
104
Characteristics of an Ideal Dehydrating Agent
1. It must dehydrate tissue rapidly without producing considerable shrinkage or distortion
2. It should not evaporate very fast
3. It should be able to dehydrate even fatty tissues
4. It should not harden the tissues excessively
5. It should not be toxic to the handler
105
As a general rule, the amount of dehydrating agent used should not be _____ the volume of the specimen in order to ensure complete penetration of the tissue.
less than 10 times
106
Three solutions commonly used in dehydration
Alcohol, acetone, dioxane
107
Methods/Solutions used in dehydration
**Alcohol Method**
**Acetone Method**
**Dioxane Method**
**Tetrahydrofuran (THF)**
**Cellosolve (Ethylene Glycol Monoethylether)**
**Tri-ethyl Phosphate**
108
T or F: The more delicate the tissues, the _higher_ the grade of alcohol suitable for commencing dehydration and _larger_ intervals should be between the strengths of the _ascending_ alcohols.
F. lower, smaller, ascending
109
Consists of passing the tissue through a series of progressively more concentrated alcohol baths.
Alcohol Method
110
Used for more urgent biopsies.
Acetone Method
111
A unique reagent which has the property of being miscible with both water and molten paraffin wax. It is an excellent dehydrating and clearing agent
Dioxane Method (Diethylene Dioxide)
112
Used as both dehydrating and clearing agent of tissues since it is miscible in both water and paraffin. It dissolves many substances inclusing fats and is miscible with lower alcohols, ether, chloroform, acetone, benzene and xylene
Tetrahydrofuran (THF)
113
Causes less shrinkage and easier cutting of sections with fewer artifacts. It does not dissolve out aniline dyes.
THF
114
Used bec of ots rapid action withoug producing overhardening and distortion of tissues
Cellosolve (Ethylene Glycol Monoethylether)
115
Removes water very rapidly and produces very little distortion and hardening of the tissue. It is soluble in alcohol, ether, benzene, chloroform, acetone and xylene. It produces minimum tissue damage
Tri-ethyl Phosphate
116
The process of removing alcohol from section of tissue by immersing then in ante-medium. During this process, the tissue becomes usually transparent as a result of the ante-medium rasing the refractive index.
Dealcoholization or Clearing
117
Characteristics of a Good clearing agent
1. It should be miscible with alcohol to promote rapid removal of the dehydrating agent from the tissue.
2. It should be miscible to paraffic wax and/or mounting medium to facilitate impregnation and mounting of sections
3. it should not produce excessive tissue shrinkage and hardening
4. It should not evaporate quickly in water bath
5. It should make tissues transparent
118
Most common clearing agents
**1. Benzene**
**2. Chloroform**
**3. Xylene (Xylol)**
**4. Toluene**
**5. Cedar Oil**
**6. Clove Oil**
**7. Oil of Bergamot**
**8. Oil of Origanum**
**9. Oil of Wintergreen**
**10. Carbon Disulfide**
**11. Carbon Tetrachloride**
**12. Carbol-xylene **
**13. Tetrahydrofuran**
**14. Terpincol**
**15. Phenol**
**16. High Test "Aviation Lead-Free Gasoline"**
119
Recommended claering agent for routine work
Benzene
120
One bath is needed. It is miscible with absolute alcohol (74 O.P. spirit)
Chloroform
121
Colorless. Clearing agent recommended for urgent biopsies
Xylene (Xylol)
122
Clearing agents recommended for routine work
1. Benzene
2. Chloroform
3. Toluene
123
One bath is required. It is miscible with absolute alcohol.
Toluene
124
Recommended clearing agent for CNS, skin, smooth muscle and cytological work. Two baths are required. It is miscible with 95% alcohol.
Cedar Oil
125
Recommended clearing agents for skin and smooth muscle
Clove Oil
Oil of Bergamot
126
This Spanish hop oil or thyme oil, or mixtures of these two, with or without turpentine. Recommended clearing agent for skin.
Oil of Origanum
127
Recommended clearing agent for delicate tissues. Methyl salicylate; artificial oil.
Oil of Wintergreen
128
clearing agent recommended for smooth muscles
Carbon Disulfide
129
clearing agent recommended for friable tissues. It is made by adding anhydrous crystals of phenol to xylene until no more dissolves
Carbol-xylene
130
clearing agent that is good for moist and humid climates but is corrosive
Carbol-xylene
131
clearing agent in which 3 baths are required. Is recommended for cellular organs, friable tissues, skin, atheromatous arteries, and hard collagenous specimens.
Tetrahydrofuran
132
Recommended for delicate material esp. eyes.
Terpincol
133
A colorless liquid having a boiling point of 65°C, a freezing point of -108.5°C and a density of 0.8894. It is a wide range solvent (including fats) and is soluble in most solvents.
Tetrahydrofuran
134
Clearing agent recommended for smooth muscles.
Phenol
135
An excellent clearing or dealcoholization agent.
Hight Test "Aviation Lead-Free Gasoline"
136
\_\_\_\_\_\_,\_\_\_\_\_\_\_,\_\_\_\_\_\_\_\_\_ are High Test "Aviation Lead-Free Gasoline clearing agents that cause the least hardening of tissues.
Cedar oil, gasoline, petroleum ether.
137
Methods of Embedding
Paraffin Method of Embedding
Celloidin Method of Embedding
Gelatin Method of Embedding
Vacuum Embedding
Double Embedding Method
Plastic Embedding
138
Employed as embedding medium for friable specimens and tissue fragments requiring frozen section. This method does not require dehydration and clearing process.
Gelatin Method of Embedding
139
Simplest, most common, and best embedding medium for routine processing
Paraffin Method of Embedding
140
Used for ultrathin sections for electron microscopy
Plastic Embedding
141
This is the process in which tissues are first infiltrated with celloidin and consequently embedded in paraffin. This is used to facilitate cutting large blocks of dense firm tissues like the brain. They are recommended for making small sections of celloidin blocks.
Double Embedding Method
142
Useful embedding medium for hard or friable specimens; for neurologic works
Celloidin Method of Embedding
143
A purified form of nitro-cellulose (gun cotton) and is normally supplied as a wool or in shreds moistened with alcohol and is used in 3 concentrations. It is dissolved in equal parts of ether and alcohol
Celloidin
144
Impregnation with wax under negative atmospheric pressure
Vacuum embedding
145
Embedding mediums used in Plastic Embedding
1. Butylmethacrylate
2. Epoxy resins
a. Epon resins
b. Araldite
c. Maraglass 665
d. Vestopal-W-polyester resin
146
Micture of di-tri-epoxides formed by the condensation of epichlorohydrin and glycerin.
Epon resins
147
Enumerate: Molds for Embedding
1. Leuckhart's Embedding Mold
2. Plastic Ice Trays or Cups
3. Compound Embedding Unit
4. Watch Glasses
5. Paper Boat
6. Peel-a-Way
7. TIMS
148
These are convenient molds for routine work and are widely used. They consist of 2 L-shaped pieces of metal, usually brass and are purchased in a variety of sizes.
Leuckhart's Embedding Mold
149
The molded plastic capsules come in 2 sizes. Consists of 3 pieces: a perforated bottom, a frame centerpiece, and a perforated lid.
TIMS
150
Once the wax has solidified, the plastic walls are peeled off one at a time, giving perfect blocks that requires no trimming. They can be placed directly in the chuck of the microtome.
Peel-a-Way
151
Consists of a series of interlocking plates resting on a flat metal base, forming several compartments. It has the advantage of embedding more specimens at a time, thereby rendering the time needed for blocking.
Compound Embedding Unit
152
These are ideal for embedding fragmentary biopsies.
Watch Glasses
153
These forms are convenient molds for the busy routine laboratory.
Plastic Ice Trays or Cups
154
These maybe made from a thick paper or cardboard paper. They have the advantages of being cheap to make and allowing blocks to be stored without being removed. They provide easy and accurate identification of specimens, thereby avoiding confusion and interchange of tissue blocks.
Paper Boat
155
2 Stages of manual sharpening of knives
1. Honing
2. Stropping
156
The process of grinding the cutting edge of the knife on a stone to acquire an even edge.
Honing
157
Direction of Honing
Heel-to-Toe
158
Its purpose is to remove the "burr" and to polish the cutting edge
**Stropping**
159
Direction of Stropping:
Toe-to-Heel
160
Lubricants for Hones
1. **Soapy water**
2. **3 in 1 oil** (a micture of three oils: _animal_, _vegatable_ and _mineral_)
3. **Mineral Oil USP (Liquid Paraffin BP)**
4. **Castor Oil**
5. **Clove Oil**
6. **Xylene**
161
Most recommended Types of Hones:
**1. Arkansas**
**2. Belgium Yellow**
**3. Fine Carborundum**
**4. Plate Glass**
162
Convenient size for the hone
8 x 3 inches
163
An artificial stone with more of a polishing effect than Belgium Yellow
Arkansas
164
A natural sandstone set into a slate backing. This is the best hone for manual sharpening
Belgium Yellow
165
The bite given by this is similar to that of the Belgium Yellow
Plate Glass
166
An artificial stone with much coarser bite than either the Belgium Yellow or the Arkansas. It is only used for badly nicked knives, which should then be finished on one of the other hones.
Fine Carborundum
167
This solution is irritating to the skin causing allergic dermatitis
Formaldehyde
168
It is used for thin and ultrathin sections for plastic embedding.
Paraformaldehyde
169
It preserves cellular and plasma protein better.
Glutaraldehyde
170
It forms an insoluble suboxide precipitate and is poor for glycogen fixation.
Chromate Fixative
171
Used mainly for Mucopolysaccharides
Lead Fixatives
172
Used in 3% aqueous solution. It is a strong fixative for certain lipids.
Potassium Dichromate
173
It is a strong protein precipitant and preserves carbohydrates.
Chromate Fixative
174
Best fixative for Glycogen
Picric Acid
175
Lyses red blood cells and causes considerable shrinkage of tissues
Picric Acid Fixatives
176
Fixes and precipitates nucleoprotein. It precipitates chromosomes and chromatin materials which makes it more useful in nuclear studies.
Acetic Acid Fixative
177
Recommended for phosphates and lipases studies.
Acetone
178
Destroys mitochondria and Golgi elements and causes considerable swelling of tissues.
Acetic Acid Fixative
179
Used for fixing brain tissues for rabies.
Acetone
180
Fixes conjugate fats and lipids permanently by making them insoluble during subsequent treatment with alcohol and xylene.
Osmium Tetroxide Fixatives
181
It does not preserve thick slices of tissues thus not to be used for more than 1cm thick specimen sections
Formol Sublimate
182
It is recommended for tissues to be stained by one of the trichrome technique
Zenker's Solution
183
Prolonged fixation of tissue in this produces brown scum and may cause lysis of RBCs.
Zenker's Formol (Helly's Fluid)
184
It is excellent for preserving nuclear elements (chromosome) and permanently preserves fats.
Flemming's Fluid
185
It is extremely rapid, probably, the most rapid of all fixatives.
Carnoy's Fluid
186
It gives better nuclear fixation than Flemming's Fluid.
Bouin's Fluid
187
Only a small amount of fixative is required, 5-10times the bulk of the tissue.
Champy's Fluid
188
It is more penetrating than Chromium fixatives.
Regaud's Fluid (Moller)
189
It demonstrates Rickettsia and other bacteria and preserves myelin better than buffered formalin.
Orth's Fluid
