•290 Urethral Sjnrochaetoxi.s 
Fantham (1909) also has emphasized the morphological variations of 
spirochaetes. 
Wolbach (1914) in recording some investigations on the cultivation 
of filterable spirochaetes, including one species found commonly in 
the human intestine, points out the cultural resemblance of these 
organisms to bacteria. In the case of those spirochaetes that can be 
cultivated therefore bacterial methods of differentiation might be of 
assistance. It is probably only in this way that mixed infections 
could be resolved and the risk of including in one description two or 
more dissimilar parasites entirely eliminated. 
With regard to measurements of length the system of stating the 
range between the maximum and minimum observed in preparations 
obtained from various patients at different stages of the infection can 
commend itself to but few. Logically this method would include 
the minutest forms produced by the elongation of a coccoid body 
and the longest compound forms such as those measuring 140/a found 
by Pollard in hospital gangrene. It would be more satisfactory to 
adopt as the length characteristic of the organism the length of the 
most common forms, this being equivalent to the bacteriological method 
of taking the average size of the organisms in a recent healthy culture. 
In the case of spirochaetes that can be cultivated this method would 
present no difficulties, and in others an approximation could be arrived 
at by measuring a large number of individuals and distributing them 
according to length much as is done in the case of trypanosomes. By 
measuring a large number of the spirochaetes in any particular case 
and plotting their lengths it would be possible to determine from an 
examination of the curve they formed whether it was a single organism 
or a mixed infection that was being dealt with. 
The difficulty of deciding what is the characteristic length of a 
spirochaete was exemplified in the case of an organism I cultivated 
from the blood of a guinea-pig (1914)^. This parasite varied in length 
from Ip to 35/x in different cultures at different stages, but in recently 
inoculated tubes (53 hours) in which the organism was growing actively 
they were much more uniform, the crest of the curve of measurements 
^ In view of the discovery of a somewhat similar spirochaete, S. icterohaemorrhagiae, 
in Weil’s disease it is of some interest to recall that this guinea-pig was supposed to have 
been dying of yellow fever at the time the blood culture was made. The suggestions 
of Schaudinn and of Novy that yellow fever might be due to a spirochsiete, the position 
of 8. interrogans described by Stimson, and the possibility that Seidelin’s Paraplasma 
flavigenum might be a stage in tbe development of a spirochaete, deserve further con¬ 
sideration. 
