APPENDIX 479 



and finally, two or three other animals are inoculated intra-peritoneally 

 with the semi-liquid substance obtained on mixing together the two 

 layers into which the butter was formed. At the end of expiration of 

 seventy days the animals which have not already succumbed are 

 sacrificed, and a careful post-mortem examination is made. Microscopic 

 preparations and cultures are made from any organs affected. The 

 latter, taken together with the general aspect of the lesions, will, in the 

 majority of cases, be sufficient to enable a diagnosis to be made between 

 the true bacilli of tuberculosis, and other acid-fast organisms resembling 

 it. Bacilli which resists in a moderate or somewhat feeble manner 

 decolorisation by acids, which develop rapidly at a temperature of 37 C., 

 and grow feebly at ordinary room temperature, which exhibit chromo- 

 genic properties in culture, and give rise in the guinea-pig to lesions 

 which are not characteristically those of tuberculosis, must be regarded 

 as organisms of the acid-fast group, non-pathogenic for man, though 

 possibly related in some degree to the true bacillus of tuberculosis (see 

 also p. 358). 



Another method is that indicated by Roth. Five grammes of butter 

 are vigorously shaken up in sterile water, and the whole is then centri- 

 fugalised. A fat-free deposit is thus obtained, and given quantities of 

 this are injected into animals in the ordinary manner. 



SPECIAL METHODS 



Examination Of Colostrum. Colostrum is the term applied to the 

 first milk yielded by the cow after parturition. It differs considerably 

 from ordinary milk, and generally appears as a thick, turbid, yellowish, 

 viscid fluid. When examined under the microscope, it is found to con- 

 tain, in addition to the ordinary milk corpuscles, peculiar conglomera- 

 tions of very minute fat granules which are hence known as colostrum 

 corpuscles. The chief chemical differences between colostrum (or 

 beastings) and milk are mainly three. First, colostrum is deficient in 

 casein. Secondly, it is proportionately rich in albumen. Thirdly, it con- 

 tains nearly three times more salts than milk. Probably it is this excess 

 of salts that usually causes it to exert a purgative effect upon the new- 

 born calf, and thus to remove the meconium which has accumulated in 

 the foetal intestine. 



The difficulties of bacteriological examination of such a subject as 

 colostrum are considerable. At the outset, a fair sample is only obtain- 

 able by adopting the following precautions : (a) The teats and udder to 

 be cleansed ; (b) milking to be carried out as soon after calving as pos- 

 sible, when the calf has sucked; (c) the first part of the "milking" to 

 be discarded, and the last part only to be examined. When the 

 colostrum reaches the laboratory, it must be diluted in precisely the 

 same manner as thick cream. After abundant dilution treat the solution 

 in the ordinary way, by staining preparations for the microscope, plating 

 out on various media, and sub-culturing. 



Bacteriological Examination of Butter. Take a quarter of a 



