BIOLOGY. 



Castle, W. E., Harvard University, Cambridge, Massachusetts. Continua- 

 tion of experimental studies of heredity in small mammals. (For previous 

 reports see Year Books Nos. 3-21.) 



During the past year the general plan of investigation outlined in previous 

 reports has been followed, to make an exhaustive study of the linkage rela- 

 tions of genes in mammals. Although several minor problems involved in 

 this plan have been solved, it seems better not to attempt a report upon them 

 at this time, but to postpone it until its bearings on general questions can 

 be more fully discussed. The breeding operations with rabbits and rats 

 have been very extensive and successful, and a number of stocks of par- 

 ticular genetic composition have been produced as the indispensable material 

 for tests of linkage relations and for other purposes. 



Two species of rat are being studied, Mus norvegicus and Mus rattus. The 

 former is the one commonly used in laboratory studies and genetically the 

 better known. But the latter promises to yield results valuable for com- 

 parison with those based on the Norway rat, the mouse, the rabbit, and the 

 guinea-pig. We already have two different varieties of gray rattus and two 

 of black, one variety of black being dominant, the other recessive in relation 

 to gray. We also have a yellow variety recessive in relation to black or gray, 

 and hope soon to obtain a blue variety reported from England and a cinnamon 

 variety reported from Texas. An albino variety is much desired for linkage 

 studies parallel with those which have been made in the Norway rat and in 

 the mouse, but at present no such variety is known. 



Upon the Norway rat studies are in progress of differential fertility in 

 relation to inbreeding, and of the effects of X-rays upon the germ-cells. In 

 rabbits a study is being made in cooperation with serological experts of the 

 Massachusetts Department of Public Health, to discover if possible whether 

 blood groups occur similar to those reported to occur in man and, if so, how 

 they are inherited. Results so far are negative, but the experiments will be 

 extended to wild species of rabbits as well as the domestic species. 



Kofoid, Charles A., University of CaUfornia, Berkeley, California. Investi- 

 gation on intestinal protozoa. (For previous report see Year Book No. 21.) 



Investigations have been continued on the incidence of human amcebiasis 

 and Arthritis deformans of Ely's second type, in collaboration with Dr. L. 

 M. Boyers and other physicians having clinical charge of patients suffering 

 from this disease. The work is conducted with a view to the clearer defini- 

 tion by the physician of the clinical signs of the disease, and on our part by 

 a clearer characterization of the types of amoebae associated with the disease. 

 Gratifying results in the detection (by persistent and repeated examinations) 

 of a small form of amoebae have been obtained. There are indications that 

 there is a high degree of resistance established in the cases of supposed bone- 

 marrow infection with resulting involution or dwarf stages of the parasite. 



We have examined additional cases of Hodgkin's disease, with the result 

 that in every instance but one there is accompanying amcebiasis of the bowel. 

 In this one instance only a single specimen was available for examination. 

 Some of these cases have been under treatment and observation with grati- 

 fying results to date. 



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