The President's Address. By G. S. Woodhead. 119 



contents of patients suffering from cholera, but, as he found 

 them only when the patient had taken beer, and being a wise 

 and observant man, he wrote them down as having no special 

 significance in relation to the disease 



Then came the work of Bassi(1837),* who made a real advance 

 for us by his careful study of silk-worm disease (muscardine), 

 with which he found associated a vegetable organism or fungus, 

 whose spores appeared to be exceedingly infective even for healthy 

 caterpillars These spores were transferred by direct contact or 

 by currents of air from the affected to the healthy larvse, germinat- 

 ing on the skin, making their way inwards, and so producing the 

 specific disease. Bassi thus was able to demonstrate that the 

 lower plants are capable of living parasitically on animals as well 

 as on plants. Others, also, seem to have been greatly occupied 

 at this period with the question of parasitism, for we find that 

 just about the same time the itch mite, Acarus scabei — which had 

 been described by the Cordovan physician, Avenzoa (died 1164), 

 and then forgotten until Bernard de Gordon, a Scottish physician 

 who taught in Montpellier at the end of the thirteenth and 

 beginning of the fourteenth century, re-discovered it, though it was 

 again lost sight of for centuries — was again " re-discovered " and 

 brought into prominence as the cause of itch. 



All these important observations made in the thirties of the 

 nineteenth century drew attention to the question of the exist- 

 ence of a living contagious agent, the contagium animation, and 

 Jacob Henle (1840), histologist and microscopist, summing up the 

 evidence at his disposal,! concluded that the contagia of diseases 

 carried by air currents, as well as of those resulting from direct 

 contact with patients suffering from contagious disease, must be 

 living organisms, capable of continued, and probably independent, 

 existence, for some time at least, having the power of multiplying 

 and able to produce special substances, poisons or ferments, that 

 act upon animal tissues, altering their functions or bringing about 

 their disintegration. He realized that it might not be the animal 

 or vegetable organisms themselves, but their eggs or spores that 

 constituted the infective agent. He pointed out, however, that the 

 mere presence in the excretions or degenerated tissues of patients 

 suffering from disease of either the organisms or their spores did 

 not afford adequate proof that these organisms or spores were the 

 infective factors in the " contairia " as he called them. How wide 

 and, at the same time, intensive was his outlook is evident when 

 we realize that he foreshadowed the postulates deemed necessary 

 by Koch for the proof of the connexion between a possible con- 

 tagium and a definite disease. He insists that the demon- 

 stration of the presence of an organism in the lesions or tissues 



* Del mal del segno, calcinaccio o rnoscardino. Sec. ed. Milano, 1837. 

 t Pathologische Untersuchungen, Berlin, 1840. 



