1883.] On the Infectivity of the Blood and other Fluids, 455 



forty hours ; here obviously there is no appreciable shortening of the 

 incubation* period; but the instances recorded show how constant in 

 the large majority of cases this period is, the quantity used for inocu- 

 lation is absolutely without any influence upon it, whether some 

 drops, or the hundred-millionth of that quantity is used ; it is even 

 seen frequently that inoculation with materially smaller quantities of 

 the same blood produces death in a shorter period than larger quan- 

 tities do, in such cases it would appear that the result can only be 

 owing to a difference in constitutional vigour, the power of resisting 

 infection, in the animals experimented upon. It must be remarked, 

 too, that the apparent variation in the length of the incubation 

 period as recorded herein, appears sometimes greater than was 

 actually the case, for when an animal died, e.g., during the night, it is 

 recorded as having occurred " within " a certain time, whereas it 

 may have occurred, and in some instances certainly did so, some hours 

 previously; if the death of all the animals had been actually wit- 

 nessed, this period would appear even more uniform than it does 

 here. 



In all these cases the appearances on death above mentioned were 

 observed without material variation, and in every case there were 

 found in the blood large numbers of a microphyte which is very cha- 

 racteristic and distinctive ; yet although some previous writers have 

 clearly recognised its presence, regarding it as constituting the 

 active contagium and materies morbi, no accurate account of its micro- 

 scopical characters has been given, nor its direct relation to the infec- 

 tive virulence of the blood which it infests considered. f 



This microphyte is somewhat minute and in fresh preparations 



* I have here used the term " incubation period " in the same manner as done by 

 Davaine and others, not in its proper sense of denoting the period between infection 

 and the first appearance of any symptoms of disturbance, but in reference to the 

 duration of the malady between inoculation and the death of the animal ; this, 

 though not strictly correct in the proper signification of the term, may, perhaps, be 

 excused, inasmuch both as the first occurrence of any constitutional disturbance is 

 not well marked nor easy to recognise, in the animals the subjects of these experi- 

 ments, and also as the period between the appearance of such symptoms and subse- 

 quent death is, in ordinary cases, very short, seldom exceeding a few hours. 



f MM. Coze and Feltz, indeed, described and figured a microbe which they found 

 in the cases they examined. If their figures are drawn to scale, this cannot be the 

 same bacterium here in question, or otherwise the figures are erroneous, for they re- 

 present a form fully double in breadth that which I have obtained, and more nearly 

 resembling the common septic ferment, B. termo (Cohn), than any other species 

 with which I am acquainted. If, however, these cases were examined immediately 

 after death, as stated, this form could not have developed, being a septic and not a 

 pathogenic species, nor capable of multiplying or subsisting in the tissues of the 

 living animal. It must, however, be remembered that at the time of their observa- 

 tions, nearly twenty years since, the available microscopical appliances were greatly 

 inferior to what we now possess. 



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