4 BULLETIN 1090, U. S. DEPARTMENT OF AGRICULTURE. 



Toward the latter part of the year 1896 it became evident that I would be able to 

 move the experiment station from Benning Road and Eighteenth Street to some 

 larger and more desirable place; hence I concluded that it would be wise to save as 

 many young and vigorous pigs for breeding purposes as possible, and to start the guinea- 

 pig pens at the prospective new station with this young stock. 



A new place for the station was found at Bethesda, Md., its present site, in May, 

 1897, but it was not ready to be occupied until the following November, during which 

 month the whole stock of guinea pigs was moved from Benning Road to Bethesda. 

 The stock at that time consisted of about 300 old breeders and about 400 young ani- 

 mals, unbred but specially selected for breeding purposes, also 100 to 150 young pigs. 



During the journey from Benning Road to Bethesda, Md., a distance slightly more 

 than 11 miles, a sudden, unexpected, heavy, cold shower of rain occurred, and many 

 of the guinea pigs, though they were in cages and in a covered wagon, got thoroughly 

 wet. 



From 10 days to 2 weeks later the guinea pigs began to die at the rate of from 30 to 

 50 a day. The disease which caused the deaths was a combination of inflammation 

 of the bowels and lungs. When the outbreak finally terminated just 63 guinea pigs 

 were left alive, and of them 9 were in such hopeless condition that they were killed. 

 This left 54 guinea pigs, varying in age from a few weeks to about 2 years. 



The 54 guinea pigs are the stock to which all the guinea pigs that are now in the 

 breeding pens at the experiment station, or that ever have been in the guinea-pig 

 breeding pens at the Bethesda station, trace their origin. 



The method of raising guinea pigs at the station has been always to select the best 

 animals for breeding purposes, not only with reference to size and weight, but also 

 with reference to smoothness of hair and productivity. 



Unprolific breeders have always been eliminated from the pens as quickly as pos- 

 sible, and the progeny of such breeders have always been carefully avoided in select- 

 ing fresh breeders. 



The total number of guinea pigs produced since the latter end of 1897 and the present 

 time I can not give without spending several weeks searching our records. At present, 

 however, the station is producing about 12,000 guinea pigs per annum, all of which 

 trace their ancestry back to the 54 which were left after the disastrous outbreak of 

 disease in the year 1897. 



To judge from the information I have been able to obtain from various persons who 

 are informed about guinea pigs, the stock we have at the station, so far as health, vigor, 

 and productivity are concerned, in spite of the inbreeding to which they have been 

 subjected, is, strictly speaking, very superior. 



The beginning of the inbreeding experiment is described as fol- 

 lows in a report by Dr. E. H. Riley: 



Investigations were begun in July, 1906, to study the effects of inbreeding when 

 continued for successive generations. Guinea pigs were selected for this work because 

 larger numbers could be housed and cared for with greater convenience than any other 

 animal at our disposal, and, being prolific breeders, the data from succeeding inbred 

 generations accumulated rapidly, thus enabling one to draw conclusions in a compara- 

 tively short time . Since large numbers of guinea pigs are used annually in the bureau 

 laboratories, all stock which has served its purpose in the breeding experiment is 

 readily made use of. 



Two inbreeding tests were planned in this experiment. In Test No. 1 the founda- 

 tion stock was line-bred for 12 years at the Bureau of Animal Industry Experiment 

 Station. This foundation stock was selected from a group of 150 guinea pigs. The 

 largest and most vigorous individuals of both sexes were selected for breeders. No 

 attention was paid to color or color markings, except that no albinos were selected. 



