1913] Sweet: EpUhelioma of the Common Fotul 43 



of these four developed a cold exactly similar to the one present 

 in the original hosts, in addition to the lesions of epithelioma 

 contagiosum. Eight other cockerels inoculated with the same 

 virus except that it had been passed through healthy cockerels, 

 were entirely free from any symptoms of a cold. 



COMPLEMENT FIXATION 



From the fact that an immunity is developed, it occurred to 

 us that during the course of the disease there might be a specific 

 antibody developed in the blood. Following this idea we carried 

 on complement fixation tests on the blood of normal and infected 

 fowls. 



Preparation of Material. — After the usual manner, rabbits 

 were immunized against the red blood cells of sheep, and the 

 haemolytic amboceptor thus obtained titrated and preserved in a 

 dark place. An antigen was prepared from the tumors produced 

 on the combs of fowls by epithelioma contagiosum, and from the 

 liver of a fowl having epithelioma contagiosum, after the method 

 of Michaelis and Lisser. Fresh complement or alexin was ob- 

 tained daily by bleeding guinea pigs. Blood was taken from a 

 sheep every other day, defibrinated, centrifuged, and the cor- 

 puscles washed four times in physiological salt solution. Blood 

 was taken from normal and diseased fowls iinder as nearly as 

 possible aseptic conditions and allowed to stand on ice for from 

 12 to 24 hours. The clear serum was then pipetted off, and in- 

 activated for 30 minutes at 57° C. in a water bath. After care- 

 ful titration of the alexin amboceptor and antigen, the factors 

 of our haemolytic system were now assembled and were mixed 

 according to table No. 3. 



Technique of Bleeding Fowls. — The technique used in ob- 

 taining the blood from the fowls may be of interest, because 

 we have not been able to find a similar method described in the 

 literature, and it was only after trying several unsatisfactory 

 methods that we hit upon this method. It is not necessary to 

 kill the fowls, as considerable quantities of blood can be taken 

 without damaging the bird, and the.y can be bled rather fre- 

 quently as the.y show marvelous powers of recuperation. Even 



