Leukemia 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. 
Stgns 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 
