538 



Pathological Significance of Nematode Hcematozoa. [part hi. 



Whether this tube is the old cuticular covering of the embryo, which parasites of this 

 kind are known to cast oif during the process of development, and which, under this 

 altered condition, becomes more permanent (for it can hardly be supposed that the 

 blood is the natural habitat of this parasite, seeing that no very evident developmental 

 changes take place), or whether it be merely the dilated, attenuated covering with 

 which the embryo was originally invested, I am unable to decide.* As the cyst 

 invests the parasite very closely laterally, and is, to some extent at least, elastic, 

 there is frequently some difficulty in distinguishing it from the body of the worm 

 proper, especially when, as is usually the case, the fluid in which it is found contains 

 molecular matter which obscures the minute structure of the parasite ; or when death 

 occurs, as is commonly the case, whilst the worm is fully extended, and it thus 

 occupies the whole length of the tube. During life, however, when the movements 

 are not too rapid, and the field is cleared of molecular matter, the saccule may, as far 

 as my own experience goes, — and I have examined some thousands of specimens, — 

 always be distinguished if the microscope be good and the illumination properly 

 adjusted. 



Fig. 34. — The Canine Haematozoon and three red blood-corpuscles fixed in serum by osmic acid. The clear space 

 alongside the parasite is owing to the removal of the film of serum by contraction of the worm, x 600. 



On one occasion it seemed as though I had succeeded in detecting such a cyst 

 in the canine Hsematozoon — a lifeless specimen immersed in fluid, but subsequently it 

 was found that the appearance observed was due to the specimen having been torn 

 across a short distance from the caudal end; the granular substance of the worm had 

 escaped at the part, thus leaving a hyaline tube (containing, however, a few oil 

 molecules) formed by the investing membrane proper of the worm : the detached 

 fragment was subsequently found on the same slide. 



When specimens of the blood of the dog infested with these parasites are spread 

 out in very thin layers upon glass slides and subjected to the fumes of osmic acid, 

 in the maimer recommended on a former occasion in connection with the Filaria 

 sanguinis hominis, a deceptive appearance is frequently produced by the contortions 

 which the worms may undergo during the process of "setting" of the serum. A 



* Since this was written, I have observed that Schneider has suggested a somewhat similar explanation with 

 reference to the capsule which appears to envelop the young of Ichthyonema globicej>s : " Embryonen von 

 einer Hiille umgeben, ob dieselbe durch Hautung oder durch Erweiterung der EihUUe entsteht, ist ungewiss" — 

 Monographie der Nematodeu, s 175. 



