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THE POPULAR SCIENCE MONTHLY. 



so prominent in all the primitive religions 

 of the world that it has completed the cir- 

 cuit of the habitable globe. As such they 

 form an important item in the evidence to 

 establish the fact that the symbolism em- 

 ployed by the ancient inhabitants of this 

 region was far too refined and abstract to 

 have been the outgrowth of the religious 

 ideas of savage hunters and warriors ; and 

 that it bore a close analogy to, if not abso- 

 lutely identical with, that in use among the 

 nations of the central part of the continent 

 when invaded by the Spaniards." In one 

 of the forms of the figure, the sun is marked 

 with a cross, thus giving new evidence of 

 the universality of that symbol among man- 

 kind. 



The Bacilli of Tubercle. The "Medi- 

 cal Press " gives one of the clearest accounts 

 of the experiments by which Dr. Koch has 

 established the bacterial origin of tubercle. 

 In pursuing his investigations, Dr. Koch 

 used material derived both from human and 

 animal sources. Examination of the tuber- 

 culous material deposited in various organs 

 led to the discovery of minute organisms 

 possessing all the bacterial characteristics 

 of bacilli, whence the conclusion was formed 

 that those forms of life are invariably pres- 

 ent in such deposits. In a multitude of 

 cases of miliary tuberculosis, bacilli in in- 

 calculable numbers were encountered in 

 every affected situation, and the conclusion 

 was warranted that they inevitably accom- 

 pany the development at least of the disease. 

 To demonstrate, however, that they are the 

 cause of the affections, required the ac- 

 cumulation of sufficient actual proof, and 

 Koch's claim to the gratitude of the world 

 rests on the fact that he appears to have 

 made this. Numbers of Guinea-pigs, rab- 

 bits, and cats were operated upon, with the 

 result, in every case, of verifying the con- 

 clusions which the experimenter had reached. 

 By directly transferring the tuberculous mat- 

 ter from diseased animals to healthy ones, 

 through inoculation, Dr. Koch succeeded in 

 all cases in reproducing the disease. As, 

 however, it was still possible that the con- 

 tamination might be due to a virus con- 

 tained in the transferred material, rather 

 than to the presence of microscopic organ- 

 isms in it, " cultivation " experiments were 



introduced and conducted on a very exhaust- 

 ive scale. A pabulum was found in which 

 the bacilli grew and reproduced freely. By 

 repeated sowings in new quantities of the 

 nutritive matter, extending in some cases to 

 six months, a generation of " purified " ba- 

 cilli was obtained which could not by any 

 possibility be accused of communicating 

 virus. When these organisms were intro- 

 duced into healthy animals, they never failed 

 to reproduce themselves in incalculable 

 numbers, and to set up all the symptoms of 

 tuberculous infection. Thus, four Guinea- 

 pigs were inoculated with bacilli of the fifth 

 generation produced in fifty-four days from 

 tuberculous matter originally derived from 

 a human being. In each case the infected 

 animal sickened and lost flesh, and was 

 found when killed to have strongly pro- 

 nounced tuberculosis. This took place what- 

 ever was the point in the body chosen for the 

 injection of the infective material. When 

 some animals were injected with healthy 

 blood-serum at the same time that others were 

 inoculated with bacilli, the latter sickened 

 and became tuberculous, while the former 

 were not affected. In another series of ex- 

 periments the sputum of phthisical patients, 

 even after having been thoroughly dried, 

 was found to produce similar effects with the 

 bacilli. Certain conditions seem essential 

 to the development of the bacilli under the 

 ordinary circumstances of communication, 

 and further experiments will bear reference 

 to ascertaining precisely what they are. 



Neglect of the Study of Insanity. In a 



paper read before the National Association 

 for the Protection of the Insane and the 

 Prevention of Insanity, Dr. Nathan Allen, 

 of Lowell, Massachusetts, calls attention to 

 the neglect in which the study of insanity is 

 left by the medical profession generally. 

 Acknowledging that the study of the func- 

 tions and disorders of the brain presents 

 more difficulties than any other branch of 

 medical science, but seemingly considering 

 this as only a stronger reason why more at- 

 tention should be given to it, he finds that 

 in very few instances is insanity mentioned 

 as one of the subjects in the annual circu- 

 lars of medical schools advertising their lect- 

 ures. In only three or four schools is there 

 a professorship or course of lectures de- 



