230 THE ORIGIN AND PROPAGATION OF DISEASE. 



ments and tlie spores. He asserted tliem to be always present in cases 

 of favus, and declared that the malady itself was essentially "nothing 

 but a vegetation." The parasite thus described proved to be the same 

 with that previously seen by Schonlein, and it was afc last definitely 

 known by the name of Achorion Schdnleinii. 



Gruby continued his examinations, and in 1844 discovered a micro- 

 scopic vegetation growing upon the skin, in a case of Porrigo decalvans ;* 

 and the same parasite, the Tricliophyton tonsurans, has since been recog- 

 nized as a constant accompaniment of Tinea sycosis and Tinea circinnata. 



Finally, Microsporoii furfur was discovered by Eichstedt, in 1846,t as 

 a parasitic vegetation in Tinea versicolor ; so that within seven or eight 

 years three distinct microscoi)ic fungi were discovered and recognized as 

 occurring in diseased conditions of the human skin. 



Now, the first question which naturally came up in relation to the dis- 

 covery was this : Is the microscopic fungus the cause of the disease, or 

 is the disease the cause of the fungus? Either of these two suppositions 

 might be the true one. In the first place, the fungus, by its accidental 

 presence and growth in the skin, might excite all the irritation aad mor- 

 bid discharges characteristic of the malady. On the other hand, its 

 presence might be altogether secondary, and a result of the morbid ac- 

 tion instead of its cause. Every vegetable requires a soil suited to its 

 growth. Tbe fungus-germs might be incapable of fastening themselves 

 upon the healthy skin, but might readily flourish in the decomposing 

 mixture of inflammatory exudations. This question, in the earlier 

 stages of the investigation, presented a real difficulty. Henle, in 1840, 

 believed thixt Achorion Bchonleinii-wix^ merely' an incidental formation in 

 the crust of favus, while Remak and others regarded it as the cause and 

 essential element of the disease. 



1^0 w, how was this difficulty to be settled"^ If Tinea tonsurans is 

 always accompanied by trichopliyton^ and if trichophyton is never found 

 upon the skin except in some form of tinea, how can we tell which of 

 these two is the cause and which the consequence of the other? 



The test of this is twofold: 1. Inoculation of the parasite and repro- 

 duction of the disease 5 2. Destruction of the parasite and cure of the 

 disease. 



Both of these tests have been successfully carried out. The inocula- 

 tion of Achorion Schdnlenii was accomplished by Remak,| in 1840, and 

 subsequently by Bennett,§ Hebra, Vogel, Bazin,|| Kobner and Deffisj 

 that of Trichophyton by Defifisff and Kobner 5** and, finally, that of 



* " Comptes Reudus de I'Acaddmie des Sciences," tome xviii, p. 583. 

 t Cited iu Robia's " Vegetaux parasites," Paris, 1853, p. 438. 

 X Cited in Robin; "Vegetanx Parasites," Paris, 1853, p. 477. 

 ^ "Principles and Practice of Medicine," New York, 1867, p. 850. 

 II "Affections cutan6es parasites," Paris, 1858, p. 56. 

 % Bazin, "Affections cntanees parasites," j). 147. 

 ** Sclimidt's " Jajirbiiclier," cxx-si, p. 260. 



