May 15, 1879] 



NATURE 



51 



different countries seem to agree with one another in all 

 their characters. It is important to note that their pre- 

 sence is not associated with the existence of any definite 

 disease. The dogs harbouring such parasites are out- 

 wardly indistinguishable from others which have them 

 not. Strange as this may seem, it is also strange that 

 the mode in which the embryo organisms gain access to 

 the blood is still involved in great obscurity. It is true 

 that, by several observers at different times, thread-like 

 mature nematodes (JFilaria immitis) have been found in 

 more or less abundance in the right chambers of the heart 

 of the dog. These have been found to be extremely 

 common by Dr. Manson in China, and might therefore 

 naturally enough be considered as the source of the multi- 

 tudes of embryo nematodes found in the blood of these 

 animals. But if true for China, it ought also to hold good 

 for India ; yet Dr. Lewis says :— " It seems somewhat 

 strange that, notwithstanding the marked prevalence of 

 embryo hamatozoa, the Filaria immitis has not, so far 

 as I can learn, been recognised in India. I have often 

 searched specially for it but in vain. The only mature 

 parasite which appears to affect the circulatory system of 

 dogs in this country is the Filaria sanguinolenta, a de- 

 scription of which, together with an account of the 

 pathological changes which are caused by it during its 

 development in the walls of the aorta and adjacent 

 tissues, was published by me in 1874."' But then, the 

 same writer adds : — "Notwithstanding the circumstance 

 that this is the only mature helminth which I have found 

 associated with the embryo hsematozoa of India, I cannot 

 believe that there is a genetic connection between them, 

 for it frequently happens that the mature worm may be 

 present in abundance unassociated with blood embryos of 

 any kind, and sometimes it is found that the latter exist 

 without any trace of the former." 



What has been said above suffices to show the very 

 considerable gaps in our knowledge concerning the life- 

 history of the Nematoid haematozoa of man and animals, 

 and also the tendency so frequently met with among 

 some observers to bridge these gaps by unsatisfactory 

 explanations deduced from a too-narrow survey of the 

 facts — a perennial source of error peculiarly common in 

 regard to this class of questions. 



Of the protozoa referred to as being found in the blood 

 of the lower animals the newest and perhaps the most 

 interesting are those now first described by the author as 

 existing in that of Rats. Being directed by the Indian 

 Government to make observations on the spirillum oc- 

 curring in the blood of patients suffering from the Bombay 

 fever, the author says : " Whilst doing this I had occasion to 

 examine the blood of a considerable number of animals, 

 and eventually (July, 1877) detected organisms in the 

 blood of a rat which, at first sight, I took to be of the 

 nature of vibrions or spirilla." The organisms, of which 

 figures and photographs are given, are each of them pro- 

 vided with a long and very distinct flagellum, though other- 

 wise they are not very different in appearance from some 

 bacilli. Subsequent observations showed Dr. Lewis that 

 whilst such organisms do not seem to exist in the blood of 

 mice they are to be found in two species of rats, viz., Mus 

 dccumanus and Mus rufescens. Concerning their pre- 

 valence and pathological significance in these animals, he 

 ^ " The Pathological Significance of Nematode Haematoioa." 



says :— " I have examined the blood of a great number of 

 rats for the purpose of ascertaining what proportion of 

 them contains these organisms in their blood, and find 

 that of those specially examined for this purpose, their 

 existence was demonstrated in 29 per cent. Sometimes 

 however, the numbers detected were very few, not more 

 than one or two in a slide, but in the greater number of 

 cases they were very numerous, every slide containing 



several hundreds With regard to the health of the 



rats in which these flagellated organisms were detected, 

 there was nothing to suggest in any way that they were 

 less healthy than others not so affected, and I have re- 

 peatedly kept rats for a considerable time for the purpose 

 of observing whether any special symptoms would be 



manifested When it is considered that thousands 



of active beings of this character can exist in the blood 

 without in any appreciable manner affecting the health of 

 their host ; and when it is further considered that these 

 organisms must consume at least as much, if not far more, 

 oxygen than bacteria, bacilli, and spirilla, it becomes dif- 

 ficult to understand how it comes about that, to a like 

 action on the part of the latter is ascribed the asphyxia 

 and the other morbid conditions which characterise 

 death from splenic disease and allied affections." Such 

 a view has been put forward by MM. Pasteur and Joubert, 

 though it is well known, and has been pointed out by 

 Virchow amongst others, that the proportion of bacilli 

 in the blood at autopsies, bears no sort of relation to the 

 severity of the disease previously existing in the persons 

 under examination. 



But it is in regard to these vegetal organisms existing 

 in the blood of man and some animals that the larger 

 part of Dr. Lewis's memoir refers. He evidently enter- 

 tains a clear view of the principal phenomena to be con- 

 sidered in reference to this part of the subject, and exhibits 

 a rare absence of a tendency, which is unfortunately but 

 too common, to slur over fundamental difficulties stand- 

 ing in the way of the acceptance of the " Germ Theory 

 of Disease" — or the "Doctrine of Contagium Vivum" 

 as it is sometimes termed. In addition to acute criticism 

 Dr. Lewis has made known some very significant and 

 important new facts. 



After referring to the generally received view that 

 organisms of the bacterium or bacillus type do not 

 exist to any recognisable extent in the blood of healthy 

 animals, and to the experiments made some years ago by 

 Dr. Douglas Cunningham and himself, which showed how 

 quickly, after such organisms had been purposely intro- 

 duced into the blood of healthy animals, they disappeared 

 therefrom, he says : — "It may be safely affirmed that their 

 presence in appreciable numbers is, judging from ex- 

 perience, incompatible with a state of perfect health." 

 The case in regard to these microphytes is, therefore, 

 different from what has been stated to obtain with the 

 animal organisms before mentioned, which may swarm in 

 the blood of creatures who are in other respects quite 

 healthy. 



One or other of such microphytes has been found to be 

 generally present in charbon or splenic fever, and in 

 recurrent fever. M. Pasteur has of late maintained that 

 septicemia is also characterised by the existence of such 

 organisms in the blood during life; and to this list Dr. 

 Klein adds the so-called typhoid Jever of the pig. 



