310 Transactions of tlie Society. 



IX. — The Bacteria of Bavaine' s Septicaemia. 

 By G. F. DowDEswELL, M.A., F.K.M.S., F.C.S., &c. 



(Bead 10th May, 1882.) 



The organisms here shown under the Microscope, and which occur 

 in the blood of the rabbit, in the form of septicaemia known as 

 that of Davaine (one of the first who described it, about twenty 

 years ago), are remarkable, in many respects, from a microscopical 

 point of view, and possess a general interest from their relation to 

 the affection in which they occur, and which has been regarded 

 almost as the type of a specific parasitical disease, from the circum- 

 stance that the blood of an animal in these cases is infective in 

 inconceivably small quantities. The statements of Davaine on this 

 point, which attracted so much attention, were that the trillionth,* 

 or the ten-trillion th part of a drop of this blood was infective. 



His experiments were repeated by several observers, who con- 

 firmed his results in difierent degrees. I have myself found, in 

 numerous experiments, that in the case of rabbits the blood is 

 usually infective up to the millionth and the hundred-millionth 

 part of a drop ; sometimes in even smaller quantities, obtained by 

 successive dilutions. 



In such blood I have found that the organisms here described 

 always occur, but in very variable numbers ; in some cases not 

 more than one or two are to be found in each field of view, in 

 others they exceed many times the number of the blood-corpuscles; 

 they do not appear to increase in any marked manner shortly after 

 death, as is the case in some other affections. The microphyte itself 

 is a form of Bacterium, in the generic sense of the term, as defined 

 by Cohn ; its diameter, which varies less than that of any other form 

 of Schizophyte which I have examined, is just over half a micro- 

 millimetre (0 • 509 fjb), almost exactly ^^i-^u m. The length which, 

 in different stages of development, is very variable, may be put 

 down at from 1^ to 2, 3, or, in a few cases, 5 times the diameter, 

 that is, of the single cells, or rods as they are commonly termed ; 

 two or three of these, but not more, sometimes occur united together, 

 endwise, forming short chains ; but they never, in the blood of an 

 animal, form either long leptothrix filaments or zoogloea masses. 

 They frequently appear in the form of a figure of 8, or a dumb- 

 bell ; this, as is shown in stained preparations — an example of which 

 may be seen in the field of view under the Microscope — is not due 

 to a constriction of the cell-wall, indicating incipient fission, but to a 

 difference in its constituent parts and their refractive power ; the 



* A trillion in the French notation is a billion in the English, i.e. a million 

 squared. 



