574 INFECTION AND IMMUNITY. 



which he again produced tuberculosis in experi- 

 ment animals. 



The tubercle bacillus is an obligate aerobic para- 

 site, has the form of a slender, non-flagellated rod, 

 often slightly curved, from 2 to 4 microns long 

 and from 0.3 to 0.5 microns broad. In stained and 

 even in unstained specimens, when properly 

 treated, a number of spherical, oval or elongated 

 clear spaces can be seen which Koch at one time 

 thought to be spores. They are now considered 

 either as vacuoles, or as representing some form of 

 degeneration or reserve nutritious material. Spore 

 formation is uncertain. The organism is sup- 

 posed to possess a membrane which may be re- 

 sponsible for its strong resistance against heat and 

 desiccation. Feinberg speaks of a nucleus ( ?) which 

 may be demonstrated by a modified Eomanowsky 

 stain. The organism shows many variations in its 

 morphology under different conditions. It often 

 exists in isolated clumps, either in cultures or in 

 tissues, and may be excreted as such in the urine. 

 In certain cultures and sometimes in animal tis- 

 sues it grows in the form of longer or shorter 

 branching threads, in this respect resembling acti- 

 nomyces. This last occurrence has led a number 

 of authorities to class the tubercle bacillus as a 

 streptothrix, while others would give it an inter- 

 mediate position between true bacteria (schizomy- 

 cetes) and the streptothrix (a hyphomyces). Oval 

 or spherical degeneration forms, the capsules or 

 corpuscles of Schron, are found in advanced tuber- 

 culosis of the lymph glands and other organs in 

 which there is a great deal of necrosis. 



The tubercle bacillus is one of a group of organ- 

 isms which are said to be "acid fast" in their 



