RAISING LABORATORY MICE AND RATS 9 
Systemic infections.—Infectious ectromelia is an acute disease of mice, and 
often becomes chronic. In the acute stage polyserositis and acute hepatitis 
are present. In the chronic stage, edema, vesiculation, ulceration of the skin 
of the feet, and even sloughing of the feet may result. 
The salivary gland disease of rats and mice affects the ducts, salivary glands, 
and sometimes the kidneys. Inclusion bodies are present in the hypertro- 
phied cells of these organs. 
Fungus Diseases 
A white ear fungus sometimes grows on the ears of mice. It is difficult to 
eradicate. If infection is not great the affected portion of the ear may be 
clipped off. Sodium subsulfate powder will stop bleeding. Tincture of iodine 
or a 5-percent alcoholic solution of salicylic acid will hasten recovery. Badly 
infected animals should be killed. 
Cancerous Growths 
Hereditary tumors, affecting the mammae particularly, are common in cer- 
tain strains of mice. These occur mostly in aged animals. Strains of ani- 
mals have been bred for high and for low incidence of various types of tumors. 
These strains have been used extensively in research on cancer and tumor. 
PARASITES 
Mice and rats are often parasitized by one or more species of coccidia, but 
usually these animals are not seriously affected by the organism. 
Rats and mice are often parasitized by the larvae of the tapeworm of dogs 
and cats. These larvae are introduced into the animal colony in bedding or 
food that is contaminated by the feces of dogs or cats. 
Fleas, mites, and lice sometimes infest the mouse or rat colony, but seldom 
prove fatal. Pyrethrum powder or pulverized tobacco dusted on the animals 
will usually keep these pests under control. Dipping the animals in a warm, 
very dilute solution of livestock dip and drying in a warm room are also 
effective. Cages should be dipped in a solution of cresylic disinfectant. 
SELLING AND SHIPPING 
Several of the large institutions that regularly use rats and mice now main- 
tain their own animal colonies. However, many institutions depend upon 
dealers for regular supplies of strains of these animals standardized for spe- 
cial use. There are several producers of standardized strains throughout 
the country. Names of dealers and of reference books may be obtained on 
request by writing to the Bureau of Animal Industry, United States Depart- 
ment of Agriculture, Washington 25, D. C. Persons who require large num- 
bers of rats and mice prefer to purchase from well-known dealers or institu- 
tions because they are assured of a constant supply of uniform and standard 
stock. 
Many small producers of laboratory animals sell direct to the institutions 
using them or to dealers who gather up stocks to be sold to the laboratories. 
Individuals raising these animals should also communicate with the large 
hospitals and laboratories in their immediate area, as frequently such insti- 
tutions are desirous of dealing with a dependable producer close at hand. 
The Department of Agriculture does not purchase guinea pigs, white mice, 
or white rats, and has no animals for sale or for free distribution. Persons 
expecting to make large profits from the raising of laboratory animals should 
be cautious about expending too much capital, since this, like other enter- 
prises, is subject to disappointments and failures. Most of those who have 
succeeded have probably done so only after years of patience and experience. 
Prices of mice and rats vary, depending upon supply and demand, special 
purposes for which they were developed; size, age, and various other factors. 
Mice for laboratory use are usually sold from about 3 weeks of age and up- 
wards and may bring 6 to 25 cents each. Breeding stock is usually sold in 
