596 APPENDICES. 



called into question ; and had Steel studied photograplis of 

 spirilla he would not have regarded the corkscrew appearance as 

 imaginary. 



Steel found the parasite in all cases, and further observed that 

 it appeared as the temperature rose and disappeared during the 

 apyrexial periods. 



From all these observations Steel concluded as follows : — That 

 relapsing fever of mules is an invariably fatal disorder, characterised 

 by the periodical occurrence of attacks of high fever, during which a 

 special organism closely resembling the spirillum of relapsing fever 

 in man is found in the blood. This organism is one-sixth the size of 

 a red corpuscle in width and three to six times in length. It is 

 eel-hke, and, when dried and stained, presents a thick portion — the 

 body — and a spiral tail. The latter takes less of the dye than the 

 former, and commences as a sudden narrowing of the body, termi- 

 nating by a fine point. This, he insisted, had nothing of the nature 

 of an infusorian flagellum. The thick portion tapers in either 

 direction from its centre, and terminates in front abruptly in a rigid 

 process, with probably some holdfast organ. The sharpness of the 

 head end varies in different animals. The body portion he described 

 as spiral, and so closely in general appearances to resemble the 

 spirillum of relapsing fever that he concluded that the organism 

 was undoubtedly a spiral bacterium and named it after its discoverer 

 Spirochceta Evansi. This view, however, would not be accepted by 

 Evans, who maintained that, whatever it might be, it was not a 

 member of the family of bacteria. 



In the face of these conflicting opinions Evans, in 1885, submitted 

 to the author preparations of the organism in the blood as well 

 as material from the lungs and intestines of a camel that had 

 succumbed to the disease. 



On examining a stained preparation the author found that 

 with a power of 200 diameters a number of the parasites could 

 be distinguished in the field of the microscope, and with -^ and 

 y\- o. i, objectives the individual characteristics were clearly brought 

 out. These were quite sufficient at once to dispel the idea of its being 

 a spirillum. It was obvious that it was a more highly organized 

 micro-parasite, presenting very peculiar and distinctive structiu^al 

 appearances. 



The author came to the following conclusions : — 



The somewhat tapering central portion, or body, of the parasite 

 is continuous at one end with a whip-like lash, and at the other end 

 terminates in an acutely-pointed stiff filament or spine-like process. 



