2i 8 MILK AND THE PUBLIC HEALTH CHAP. 



In inoculating market milk it is very important that the 

 injection should take place as soon as possible after collection, 

 and if not possible the sample should be ice-packed. When 

 a considerable interval has elapsed after milking, and the 

 sample is not kept cool all the time, the milk not infrequently 

 contains other bacilli pathogenic to the guinea-pig, and one 

 or both the animals may die from concomitant infection, and 

 before the slower growing tubercle bacillus has had time to 

 cause any visible lesions. 



The animal test for tuberculosis takes at least three weeks 

 before any diagnosis can be made. To shorten this period 

 Bloch l has suggested that the inguinal glands on the inocu- 

 lated side should be slightly damaged by squeezing them. 

 When this was done he found that in all positive cases the 

 glands within 9 to 12 days were markedly enlarged and 

 tubercle bacilli present in large numbers both in films and 

 sections. The earlier development of tuberculosis is due to 

 the greater growth in the slightly damaged glands. 



Dold ' 2 extensively tested the question, injecting an emulsion 

 of a pure culture of tubercle bacilli into the inguinal region 

 of guinea-pigs. He found that after 9 to 12 days a striking 

 difference could be noted ; whilst the unsqueezed glands did 

 not show any, or but insignificant, enlargement, the squeezed 

 glands were enlarged to tumours of a pea or hazel-nut size. 

 He, therefore, advocates the method as a means of earlier 

 diagnosis. He remarks that the glands can be readily found 

 and squeezed. 



Joannovico and Kapsammer 3 also investigated the value of 

 this method, using emulsions containing definite and diminish- 

 ing quantities of tubercle bacilli. From their work they 

 concluded that Bloch's method enables doubtful cases to be 

 diagnosed by animal experiment within 14 days. 



In connection with animal inoculation and tuberculosis it 

 is of importance to note that the injection of dead tubercle 

 bacilli can produce tubercles and other histological lesions, 

 resembling those produced by living tubercle bacilli, and 

 differing chiefly, or even only, in their acuteness. In cases in 



1 Berlin, klin. Wochenschrift, 1907, vol. xl. p. 511. 



2 Journ. Roy. Inst. Public Health, 1909, vol. xvii. p. 560. 



3 Berlin, klin. Wochenschrift, 1907, vol. xliv. p. 1439. 



