Leukaemia of the Fowl. 21 



pieces of the organ in a mortar, after the addition of .9 per cent normal 

 salt solution. This was filtered through a single layer of fine linen or 

 a small amount of raw cotton, thus removing the fibrous tissue suf- 

 ficiently for intraperitoneal injection, although, when it was used in- 

 travenously, instant death frequently resulted. Hence it was found best 

 to filter also through two layers of filter paper with the aid of a suction 

 pump. This filtrate was found to be absolutely fiber-free, but still con- 

 tained blood and parenchymatous cells. A 15 per cent emulsion gave 

 the best results. The entire preceding process, as well as the following 

 steps, were carried out aseptically. 



The fowls were injected either intravenously or intraperitoneally 

 with 10 cc. Both methods were sometimes combined, when a total of 

 20 cc. was administered. The vein selected for injection was the large 

 one under the wing. 



Animals used for transmission were young, adult hens of the same 

 breed as the spontaneous case, and exemplified by the normal control. 



CLINICAL HISTORY. 



Incubation Period. This is usually from five to six weeks. In rare 

 cases, it may reach a maximum of 16 weeks. 



Signs and Symptoms. The onset is usually rather abrupt, preceded 

 by no definite premonitory symptoms. The animal, which has pre- 

 viously appeared entirely normal, begins to show a slight but progres- 

 sive, at times a sudden and intense, pallor of its comb, the featherless 

 area about the eyes and the wattles. This is almost invariably associated 

 with jaundice, which is likewise progressive and usually reaches an 

 extreme grade. The combination of intense pallor and jaundice results 

 in a characteristic, yellowish-pink color, which gives the fowl a ghastly 

 appearance. The comb may be surprisingly red or extremely pale with- 

 out jaundice. The animal emaciates rapidly and to an extreme degree. 

 The actual loss in weight during the disease is striking and best illus- 

 trated by the following figures. No. 28, on the day of the onset of the 

 disease, weighed 1484.5 gm. The duration of the disease was three 

 weeks, four days. At death the weight was 897 gm. Therefore, there 

 was a loss of 587.5 gm. in 25 days, or at rate of 23.5 gm. per day. 



At first the bird acts entirely normally, or it may appear slightly ill. 

 In a few days, however, it acts as if it were very sick, stops eating and 

 drinking, and stands about with head retracted, eyes closed and tail 

 drooping. It prefers to assume a squatting position. If made to move 



