278 Mr. H. G. Plimmer and Prof. J. Ptose Bradford. 



change in colour being due to the splenectomy. A few adult organisms 

 were found in the glands and in the bone-marrow. 



In the spleenless rabbit a few Trypanosoma have been found in the 

 blood on two occasions, but the animal lived nearly two months, and 

 notwithstanding the failure to detect adult flagellate forms in the 

 blood on numerous occasions, the blood was always infective, and con- 

 tained numerous forms termed " amoeboid " and " plasmodial " below. 



C. Infectivity. 



(a) In Ordinary Animals. — The blood and organs of an animal dead 

 of the disease lose, before twenty-four hours after death, their infective 

 power. This is apparently due to the rapidity with which decomposi- 

 tion sets in after death, as we have found living Trypanosoma in film 

 preparations, made as described above, as long as five to six days after 

 removal of the blood from the body; and we have also found that 

 large quantities (200 c.c.) of blood removed from the body into a 

 sterile vessel and kept in an atmosphere of oxygen, retain their virulence 

 for at least three days, notwithstanding the fact that the flagellate form 

 cannot be demonstrated. 



We have found that the blood of the dog is infective at least two 

 days before any adult Trypanosoma can be seen in the blood ; and we 

 have also found that the blood of the spleenless rabbit, in which we 

 have only on two occasions seen any adult forms, is invariably infec- 

 tive. This of course suggests the idea that the organisms must be 

 present in another form, and we have been able, by the use of the 

 method of staining described above, to demonstrate the presence of 

 other forms in the blood and organs, and have shown, by the experi- 

 ments just mentioned, that the infectivity of the blood, in cases where 

 there are no flagellate forms discoverable, depends in all probability 

 upon the presence of one of the other forms which the Trypanosoma 

 assumes. 



Although a differential staining method, such as the one we have 

 used, is necessary for following and demonstrating the various stages 

 of the life-history of the Trypanosoma, still these stages can be seen in 

 unstained living specimens, with very careful illumination. As a 

 matter of fact, our first observation of them was in unstained prepara- 

 tions. 



In the blood of the dog, cat, rabbit, rat, and mouse, besides the adult 

 forms as described above, which, as mentioned, are very various in 

 size, there are adult forms undergoing division, both longitudinal, 

 and transverse, to which reference will be made later. Also two 

 organisms are sometimes seen with their micronuclei in close apposi- 

 tion, or fused together, with more or less of their bodies also 

 merged together. Such forms we believe are conjugations. Again, there 

 are other large forms, with or without a flagellum, in which the chro- 



