HUSBANDRY, EQUIPMENT, AND PROCUREMENT OF MICE 539 



aims of proper husbandry may be attained by many methods, some expensive, some 

 inexpensive, but one should always keep in mind these aims rather than the methods. 

 Methodology is a constantly changing area but the philosophy of laboratory care of 

 mice should be much less so. 



The investigator using experimental mice should plan : 



1 . to use mice which have known lineage and uniform good health, 



2. to introduce those animals into the experimental environment only after proper 

 quarantine and observation, and 



3. to maintain them in a uniform environment with a proper diet composed of 

 known constituents under the best of sanitary conditions. 



It is with these aims in mind that we describe procedures which may be used for 

 handling, housing, and procuring mice for research purposes so that these extremely 

 useful animals may provide their fullest value to any biological experiment. 



HUSBANDRY OF MICE 



Because mice are usually handled in large numbers they are often given little con- 

 sideration as individual animals. The individual mouse determines in part the re- 

 quirements for the whole colony and as an individual is important in its relationship 

 to the population and the effect it has on it. In large colonies the attendant is often 

 referred to or considers himself as a "mouse-box changer" or some similar desig- 

 nation which implies complete lack of consideration for the mouse as an animal 

 deserving individual attention or even as a biological entity. It is therefore quite 

 important to instill in the mind of the attendant the realization that he is an animal 

 caretaker and that the animal he must care for is the mouse. 



The laboratory mouse responds as do other domesticated animals to gentleness 

 and soon becomes accustomed to routine procedures and environment. Abrupt changes 

 in these procedures or environmental conditions are as undesirable and upsetting as to 

 larger animals, although their manifestations or reactions are more obvious. The 

 first rule of good husbandry is therefore that a set routine of feeding, watering, and 

 changing of cages be established and followed faithfully. 



Feeding. 120 - 188 ' 355 ' 356> 444 ' 548, 752 ' 897 ' 898 ' 1390 — Food is usually made available 

 at all times to laboratory mice. Dry feed in the form of pellets is quite satisfactory. 

 Pellets should be a size that is easily available to the mouse through the hopper yet 

 not easily pulled from it, and their consistency should be sufficiently hard to provide 

 some wearing of the incisors. Hardness is determined by the formulation of the 

 diet and the width of the pellet. The length of the pellet is in turn determined by 

 hardness, since the usual machine extrudes compressed food which then breaks off 

 or is scraped off. 



A standardized diet for all mice or for all inbred strains of mice is desirable, but 

 unfortunately little is known about nutritional requirements ofindividual strains. Many 



