284 BULLETIN No. 161 [November. 



length. There are two well-recognized types that infect mammals, 

 the human and the bovine. The latter is shorter and thicker and 

 stains more uniformly. The avian type, found in domestic fowls 

 and birds, and a type that infects the cold-blooded animals, espe- 

 cially fishes and frogs, play almost no part in the infection of man. 

 The tubercle bacillus often presents a beaded appearance. This 

 is more common in the specimens found in old pus and sputum. It 

 is due to a fragmentation of the protoplasm. This peculiar struc- 

 ture of the organism led the earlier scientists to the belief in spore 

 formation. Koch 74 , in his first paper, Die Aetiology der Tuber cu- 

 los; held to this belief, and this idea of spore formation has found 

 place in many publications even to the present day. It is now known, 

 from the relation of these organisms to the action of heat, sun- 

 shine and chemical disinfectants, that they do not form spores 

 They are killed very readily, in thin layers, by the direct rays of 

 the sun, and also at a temperature of 60 C. in fifteen to twenty 

 minutes. In these respects they are like other nonspore-bearing 

 organisms. 



, Their power of resistance to drying and to the 



WAXY OR FATTY . - J 



SUBSTANCE antagonism of decay organisms appears to be 

 greater than that of other nonspore-bearing or- 

 ganisms, tho less than that of the spore organisms. This power 

 of resistance is no doubt due, in part at least, to the content of 

 waxy or fatty substance found largely in the outer layer of the 

 tubercle bacillus. The presence of this waxy material gives them 

 their well-known character of "acid proof" power when stained. 

 (When this waxy or fatty substance is extracted with ether, stains 

 are no longer held on treatment with an acid or alcohol.) The 

 bacillus has the largest amount of fatty substance of any known 

 micro-organism. The fat content varies, according to different in- 

 vestigators, from i o to 42 percent; while in other micro-organisms 

 an alcohol ether-extractive has been found to vary only from 1.7 to 

 i o.i percent. 



The tubercle bacillus does not secrete a soluble 

 THef 'TUBERCLE toxm > as cl B - diphtheria and B. tetani. It has not 

 BACILLUS " b een demonstrated that the tubercle bacillus forms 



a true toxin. Levene 87 proved the absence of tox- 

 albumins from extracts of the bacillus. That poisons are formed 

 is well known, tho their character is not understood. Baldwin 10 

 thinks that the symptoms and toxemia of tuberculosis are accounted 

 for by the presence of the nucleic acid products in the blood. 

 Koch 73 , Von Prudden and Hodenpyle 155 , Vissman 154 , Straus and 

 Gamaleia 144 , Sternberg 145 , Krompecher 75 , Miller 97 , and Rosenau 121 



