MILK 101 



examined microscopically, and the remainder 'inoculated 'into 

 several guinea-pigs. 



To examine the sediment microscopically for tubercle bacilli, 

 make cover-slip preparations, and either stain directly by the 

 Ziehl-Neelsen method in the ordinary way, or, preferably, stain 

 after a preliminary treatment with ether for several hours, to 

 get rid of the fat. 



Little or no reliance is to be placed on the microscopic 

 examination of the sediment from mixed milk samples for the 

 detection of the tubercle bacillus. The microscopic examination 

 of the milk from individual cows is of more value since the 

 chances of finding tubercle bacilli are greater, but a negative 

 result cannot be accepted as reliable evidence that tubercle 

 bacilli are absent. 



For inoculation purposes the method of subcutaneous injection 

 as advocated by Delepine 1 gives very reliable results. In this 

 method the injection is made subcutaneously, with strict aseptic 

 precautions, on the inner side of the leg at the level of the 

 femoro-tibial articulation. If the inoculated material contains 

 tubercle bacilli, an infection of the glands on the inoculated side 

 takes place. The popliteal, superficial, and deep inguinal, and 

 usually the sub-lumbar glands on the inoculated side are enlarged 

 (see Fig. 12), and tubercle bacilli can be demonstrated in films 

 made from them. The time at which this can be done varies 

 with the number of tubercle bacilli injected. According to 

 Delepine, with milk containing numerous tubercle bacilli definite 

 evidence of tuberculosis can be seen in animals killed after ten 

 to fifteen days ; when not sufficiently numerous to be detected 

 microscopically in the milk (i.e. a moderate number of bacilli) 

 at the end of fifteen days, and when very few bacilli are present 

 in the milk, it may be difficult to obtain any clear evidence of 

 infection before the end of the fourth or fifth week. Delepine lays 

 stress upon the importance of keeping the inoculated animals 

 isolated and under favourable hygienic conditions. For ordinary 

 work a good plan is to inoculate two animals, one being killed at 

 the end of three weeks, and the other a week or two later. 



While the pathological picture is practically conclusive of 



1 British Medical Journal, 1893, vol. II, p. 664. 



