PART III. J Nematode Worms in the Blood of Dogs. 535 



commonly been attributed to various obstructing causes, such as the pressure of 

 tumours, idiopathic diseases of nerves and vessels — doubtless in many instances quite 

 correctly so. " Nevertheless," it was maintained, " cases occurring in warm countries, 

 or in persons who had formerly resided in them, appear to indicate that the disease is, 

 probably, not dependent on such mechanical or pathological causes as these." 



Since these remarks were published, several cases of such a nature have come to 

 my notice, and all have been, when diligently inquired into, confirmatory of them in 

 the highest degree. 



Before referring to these, however, it will be more convenient to study the patho- 

 logical conditions associated with the existence of young nematode worms in the blood 

 of the pariah dogs referred to in the opening paragraph, in order to ascertain whether 

 some more satisfactory clue can be obtained by means of comparative data of this kind 

 as to the pathological significance of the human Hsematozoon here referred to, than 

 can be derived from pure inference, or from the observations concerning nematode 

 Hsematozoa generally, hitherto put on record. A rapid retrospect of such of these 

 observations as appear to be more or less closely associated with the subject may be 

 of interest to such of my readers as have not made it a matter of particular study. 



In a brief resume of the more generally known Hsematozoa among lower animals 

 which was given in the former paper, reference was made to the discovery made by 

 MM. Grrube and Delafond, more than twenty years ago, of microscopic nematode worms 

 in the blood of dogs in France.* They were about T^xjth of an inch in length with a 

 transverse diameter somewhat less than that of a red blood-corpuscle. Out of 480 dogs 

 examined, from four to five per cent, were found to be thus affected ; but on one 

 occasion only were MM. Grrube and Delafond able, by post-mortem examination, to / 

 detect parasites in the bodies of the animals, visible to the naked eye, which could be 

 looked upon as parents to the microscopic worms in the blood. On the occasion referred 

 to, however, they were able to satisfy themselves on this point by the discovery of six 

 white, filiform worms (four males and two females) in the right ventricle of one of the 

 animals. These were from five to seven inches in length and from ^jth to jV^h of an 

 inch in width ; the anatomical details could be clearly made out, as also the stages of 

 the development of the ova in the ovaries and of the embryos in the oviducts, the 1 

 embryos being considered identical with the microscopic worms in the blood. ' 



In the same paper attention was also drawn to the observations recorded concerning 

 the worms found, frequently and in considerable numbers, in the right cavities of the j \/ 

 hearts of dogs in China and elsewhere. These are commonly looked upon as iden- 

 tical with the mature examples found by MM. Grube and Delafond, and we have now 

 the high authority of Dr. Cobbold for considering those of China at least, as identical 

 with the Filaria immitis of Leidy.f 



On referring to a description of the American parasites by Professor Leidy, which, 

 by the way, in the first record we have of them, were named by him Filaria canis 

 * Caintes Rendu*, tome XXXIV, 1852, pp. 11—14. f Lancet, vol. I, 1873, p. 462. 



