272 T. R, LEWIS, 
interior of the aorta and swinging itself across the lumen - 
of the artery. I have observed the channel of the aorta 
almost entirely blocked up after death by a clot which had 
formed around a worm in this position. 
When the parasites have acquired a length of about $ths 
of an inch to an inch, and a transverse diameter of about 
=,th, they will be found to have acquired nearly all, if not 
all, the microscopical characters distinctive of the Filaria 
sanguinolenta ; and, as already mentioned, every stage in 
the development may be represented by examples of the 
parasite in the tissues of a single aorta—in the thoracic 
portion of it: I have never observed the abdominal aorta to 
be affected in this manner, nor have I observed the parasite 
in this condition in any tissue beyond the limit of the 
thoracic cavity. 
(3.) With regard to the third heading into which the 
pathological features of this phase of parasitism have been 
divided, namely, the sacculated external and scarred internal 
appearance of the aorta, it may be observed that these 
changes appear to have been produced by the development 
of the filaria as above described, by their subsequent migra- 
tion to adjoining tumours and various tissues ; and probably, 
also, by the death and subsequent softening and absorption 
of some of the parasites—an assumption supported by the 
fact that, frequently, on pricking an affected spot of this 
kind, on the walls of the aorta nothing is found except an 
accumulation of soft pultaceous substance filled with fatty 
molecules and plates of cholesterin. 
(4.) Sometimes the three foregoing classes of morbid ap- 
pearances may be found to occur in a single animal; indeed, 
the only occasion on which I observed the condition described 
under the fourth heading, now to be referred to, was also 
associated to some extent with the other three. The blood 
of a dog was found to be affected to a slight degree with 
heematozoa, and the aorta was scarred and nodulated; but 
no mature parasites could be detected anywhere, except in a 
tumour in the walls of the esophagus. Qn careful exami- 
nation of the thoracic viscera, however, a gland, or what 
seemed to be one, was observed to have become enlarged and 
softened near the origin of the left carotid artery. This 
tissue, on being cut into, was found to have degenerated 
into a pultaceous mass composed of oil molecules and plates 
of cholesterin ; but coiled in the midst of this softened mate- 
rial were five mature specimens of the Filaria sanguinolenta 
—male and female. 
This observation shows that the mature parasites, at all 
