316 



THE TUBERCLE BACILLUS 



not become confluent. After sub-cultivating three or four times, however, 

 they may coalesce to form a dried wrinkled layer. 



[(/?) The bovine type. On pure serum the 

 growth of the bovine tubercle bacillus pre- 

 sents no marked differences from that of 

 the human tubercle bacillus. ] 



(y) The avian type. The bacillus of avian 

 origin yields a more abundant growth on 

 serum than the human bacillus. The culture 

 is thick and generally has a moist, greasy 

 lustre. 



2. Glycerin agar. Except for primary 

 cultures, this is the best medium upon 

 which to grow the tubercle bacillus. A little 

 glucose may with advantage be added to the 

 medium (p. 44). 



(a) The human type. Growth begins as 

 on serum but the colonies are both larger 

 and more numerous. They rapidly become 

 confluent and form a thick, whitish, dry, 

 rough, scaly, mammilated layer even in 

 recently isolated specimens and after being 

 sub-cultivated a few times on glycerin-agar 

 the growth becomes very abundant, moist, 

 greasy and folded. When old the growth 

 has a reddish tint. 



[(/3) The bovine type. The bovine tu- 

 bercle bacillus grows much less luxuriantly 

 on media containing glycerin such as 

 glycerin-serum, glycerin-agar, or glycerin- 

 potato than the human tubercle bacillus 

 (English Commission).] 



(y) The avian type. Some authors have 

 contrasted the growth of the avian bacillus 

 on glycerin-agar with that of the human 

 bacillus. The latter, they say, gives rise to 

 a dried, wrinkled layer, while the former 

 produces a moist, fatty growth. But as has 

 been seen, the human type frequently gives 

 a copious growth of a moist, fatty appear- 

 ance : and it is equally true that the avian 

 type occasionally produces a dry, scaly 

 growth (Nocard, Grancher, Fischel). 



[" The most characteristic point of difference between the mammalian and 

 avian tubercle bacilli is that the cultures of avian bacilli are moist and easily 

 emulsified, while on most media the mammalian cultures are dry and can 

 only be broken up with difficulty " (F. Griffith, for the English Commission).] 

 3. Egg medium. A useful medium for the growth of the tubercle bacillus 

 consists of the white and yolk of eggs coagulated and sterilized by discon- 

 tinuous heating at 72-74 C. (Dorset, Capaldi, A. S. Griffith). 



Bezan9on and Griffon mix one part of uncooked yolk of egg with two parts 



[^Fig. 207 and also figs. 208, 209, 210, and 211 are from the Final Report of the 

 Royal Commission on Tuberculosis (Human and Bovine) Part II. Appendix, Vol. I. ; 

 Dr. A. Stanley Griffith by permission of the Controller of H.M. Stationery Office.] 



(a) (ft) 



4th Generation 4th Generation 



51 days old. 3 weeks old. 



FIG. 207. Tubercle bacilli of human 

 origin cultivated on glycerin-agar. (a) 

 A culture from the tuberculous mesenteric 

 glands of a child aged 8i years, who died 

 from multiple stricture of the gut (due 

 to tuberculous ulceration). The culture 

 grew moderately well on artificial media, 

 and resembled the more easy-growing cul- 

 tures of bovine origin '; it had high viru- 

 lence for the calf, rabbit and guinea-pig. 

 (6) A culture from a mesenteric gland of 

 a case of general tuberculosis originating 

 in the alimentary tract in a child aged 

 10 months. The strain grew luxuriantly 

 on media containing glycerin and was 

 only slightly virulent for the rabbit (A. S. 

 Griffith).i 



