916 Transactions of the Society. 



than to the dried and stained one, and argued that the figures of 

 spirilla like huge corkscrews must be purely imaginary, being 

 deduced from ideas of what the parasite in motion would bo like if 

 it were sufficiently enlarged. Steel, it must be observed, founded 

 these remarks upon figures in text-books and not on photographs, or 

 on a practical acquaintance with the spirillum of relapsing fever. 

 One cannot refrain from pointing out the value of photomicro- 

 graphs, for they cannot be called into question, and had Steel 

 studied photographs 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, characterized 

 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- 

 like, 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, terminating 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. 'J he body portion he described as 

 spiral, as is compatible with its diameter, and so closely in general 

 appearances to resemble the spirillum of relapsing fever as figured 

 by Ziegler, that he concluded that the organism was undoubtedly 

 a spiral bacterium and named it after its discoverer Spirochseta 

 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 Dr. Evans was good 

 enough to place in my hands for investigation some 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 I found that with a power 

 of 200 diameters a number of the parasites could be distinguished 

 in the field of the Microscope, and with 1/12 and 1/18 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 structural 

 appearances. 



