Tuberculosis 125 



as has been pointed out many times in these pages, a spotted 

 condition of the hver is no sure sign of tuberculosis. Most of 

 the other hver diseases of fowls cause a simple blotching of 

 the tissue in which the center of each spot is usually depressed 

 or at least only slightly raised (cf. Fig. 9, p. 95). In 

 tuberculosis the liver is covered with numerous raised nodules 

 varying greatly in number and size as shown in Fig. 13. 

 A section of the liver shows these nodules or tubercles dis- 

 tributed throughout the tissue. 



Still more conclusive evidence is found if the spleen is 

 covered with these same kind of nodules. The spleen in 

 health is a small rounded purplish organ about | inch in 

 diameter. It lies just above the liver in the region of the 

 gall bladder. (Cf. Fig. 7). In cases of tuberculosis it is 

 very frequently greatly enlarged and is studded throughout 

 with the yellowish-white tubercles as shown in Fig. 14. 



The lungs are rarely affected and then usually by the infec- 

 tion spreading from the liver on to the adjoining lung tissue. 

 All this agrees with the fact previously stated that fowls are 

 most easily infected through the digestive tract. 



If the post-mortem findings agree in essentials with those 

 given in the preceding paragraphs we may be practically 

 certain that we are dealing with tuberculosis. It should not 

 be forgotten, however, that the pathologist would not be 

 willing to pronounce the disease tuberculosis until he had 

 taken a small particle of the cheesy material and after stain- 

 ing this in a particular way had demonstrated by microscop- 

 ical examination that the tubercule bacilli were present. 



Some recent experiments hold out the hope that means 

 will be found for the accurate diagnosis of this disease by 

 means of some of the biological and serological tests. Van 

 Es ^ and Van Es and Schalk ^ have carried out careful experi- 



' Van Es, L., Zeitschr. f. Infektionskrank. u. Hyg. Haust. Bd. 

 14, pp. 271-296, 1913. 2 Loc. cit. 



