100 PROCEEDINGS OF THE ACADEMY OF [1893. 



INVOLUTION FORM OF THE TUBERCLE BACILLUS AND THE EFFECT 

 OF SUBCUTANEOUS INJECTIONS OF ORGANIC SUB- 

 STANCES ON INFLAMMATIONS. 



By Samuel G. Dixon, M. D. 



Prof. Robert Koch announced in 1882 the discovery of the cause 

 of Tuberculosis. He claimed that consumption was produced by a 

 peculiar bacillus of a special shape. This he described as a rod- 

 shaped micro-organism with rounded ends, either straight or curved, 

 and frequently beaded. This simple form was accepted as a con- 

 stant character until the summer of 1889, when I first observed, in 

 an artificial culture on an Agar Agar glycerin nidus, a slight incli- 

 nation to bud in one or more places along the rod, without the pro- 

 duction of any particular angle, some relations forming an acute 

 while others formed a right or possibly an obtuse angle. A single 

 bud could only be recognized with a high power objective focused 

 and illuminated with particular nicety. The indications, however, 

 were so often repeated in each field as the slide was moved upon 

 the stage of the microscope that I was sufficiently convinced of 

 the presence of branches to review the life-history of the tube in 

 which they were found and to speculate upon the factors likely 

 to have brought about the evident volution. The result was the 

 production of germs with decided branches, some of which were 

 quite as long as the parent rods or stems. This result was published 

 in the Medical Neivs of October 19th, 1889. In 1891, Prof. Allen 

 J. Smith observed branched forms of tubercle bacilli in human 

 sputum. Since then Prof. Klein, Herren Fischel, Mafucci et 

 al., have described the branching of this germ. In the summer of 

 1892 I observed the bacillus in this cycle of life in the liver of the 

 Green Jay of Mexico, Xanthoura luxosa. This discovery, coupled 

 with my observations of 1889, and corroborated by the statements 

 of other scientists, must now compel the bacteriological world to 

 recognize a more complex form of the tubercle bacillus than that 

 observed by the great German bacteriologist in 1882. Since the 

 discovery of the branched form of the tubercle germs in 1889, 

 I have been able to continuously reproduce them on artificial 

 mediums. While the young germs seem to be quite simple in form, 

 appearing in straight rods and rods bent upon themselves, those 

 which have arrived at the age of four weeks, particularly in the 



