?42 TRANSACTIONS OF SECTION D. 



3. The Adion of Atoxyl and Allied Compounds in vivo and vitro. 

 By Dr. M. Nierenstein. 



Experiments in vivo and vitro lead to the couclusion that ' Atoxyl '— jw-amino- 

 plienylarsenic acid — combines with the proteins and acts in forms of this com- 

 bination. Atoxyl does not act on trypanosomes in vitro. It is evident from the 

 experiments that this combination takes place through the NH„ group, and it is 

 never suggested that the arsenic group in atoxyl plays the role of the ' antipara- 

 sitophoric group ' (the ' trypanophobic group ' of Moore, Nierenstein, and Todd) 

 when the amido group acts as the ' antiparasito genetic group.' The proteins act 

 as ' mordants-' This explains the observations of Moore, Nierenstein, and Todd, 

 and also of Breinl and Nierenstein, that parasites when they become ' autoxyl- 

 fast' they only are so for the species and when this character has been acquired. 

 Atoxyl is secreted by the horse, as ^-aminophenylarsenic acid, p-oxyphenyl- 

 arsenic acid, and arsoxycarbamil. Those compounds are found in the hippuric 

 acid residues which were isolated from the urine bv Roaf 's methods. 



4. The Morjyhology of Piroplasma canis. 

 By Dr. A. Breinl and E, Hindle. 



Piroplasma canis is the cause of the disease known as ' malignant jaundice,' 

 which affects dogs in many parts of the world (India, Cape Colony, the Levant, 

 &c.) The infection is naturally transmitted by ticks {Hcemai)hymlis leachii, &c.), 

 but in the laboratory the strain is easily kept going by means of simple blood 

 inoculation from dog to dog. In young animals the parasites usually appear in 

 the peripheral blood about two days after inoculation. 



At early stages of the infection the parasites are large, amoeboid, and very 

 vacuolated, and usually possess only one nucleus. These forms multiply by simple 

 fission, or, occasionally, by means of budding. The large nucleus soon buds off 

 a small nucleus, which often remains connected with it by a fine chromatic line. 

 These bi-nucleate forms divide so as to give rise to two pear-shaped forms. 



At later stages of the infection, when the parasites multiply very rapidly, the 

 above described processes become somewhat irregular, owing to the extreme 

 rapidity of division. The pear-shaped division differs somewhat from that 

 occurring at earlier stages of the infection. Nearly all these latter forms are bi- 

 nucleate, and are usually somewhat smaller than the early forms. 



Occasionally the ordinary free parasites develop a very fine flagellum. 



At certain stages of the infection (before the rapid increase in the number of 

 the parasites) we have been able to trace the development of large flagellate 

 bodies. The two nuclei of an ordinary intra-corpuscular parasite swell up, and 

 the result in form somewhat resembles Leishmania. These parasites become free, 

 increase enormously in size, and develop two flagella ; they eventually assume one 

 of the two forms described below. 



1. The most frequent are large, elongate bodies, in which the large nucleus 

 appears to empty out its chromatin and become merely an achromatic residuum. 

 A varying number of small chromatic masses occur scattered through the 

 protoplasm. 



2. These are large round forms, with a large nucleus and a varying number 

 of small nuclei. The large nucleus consists of a densely staining karyosome 

 surrounded by a lightly staining area. 



Various stages in the development of these flagellate forms may be seen in 

 cultures of Pirojjlasma canis. We have been unable to follow their subsequent 

 development. 



