CYSTICUBCUS CELLULOSE, AS FOTOD IN THE MUSCLES OF THE PIG. 123 
of specimens, I found them in every possible stage of development, even in the same 
field of the microscope. I think the last class of specimens was the largest. 
Now the inference I deduce from these facts is, first, that the animals from which 
the first set of specimens were taken had some time prior to their being slaughtered been 
placed under circumstances favourable for the production of Cysticerci (most probably 
the food had contained the germs of these animalcules), but had for a certain period 
been withdrawn from them, so that all the younger animalcules—those constituting the 
vermicular stage — had been, as it were, used up to produce the adult ones; secondly, that 
those from which the second set had been taken had only been recently placed under 
such circumstances, and had remained so circumstanced up to the time that they had 
been slaughtered ; and thirdly, that those from which the third set of specimens had been 
taken, had, both some time previously, and immediately before they were slaughtered, 
been placed under circumstances favourable for the production and development of Cys- 
ticerci. Now, as to the determination and discovery of what these favourable circum- 
stances are, it would be necessary that the history of infected animals, giving similar 
microscopic indications, should be most minutely inquhed into, especially in relation to 
those different periods of the disease, and that the investigation of all these chcumstances 
should be tested by a series of careful experiments upon living animals and by examinations 
of then’ food, and all the circumstances under which they are placed, both during the 
period these animalcules are being developed in the muscles and afterwards; so that 
negative as well as positive evidence might be obtained on the subject. 
In concluding this paper, the author thinks it right to append a brief reference to 
the views at present entertained as to the nature and relations of the Cystic entozoa, in 
order that the bearing of his own researches may be more clearly apprehended. 
A similarity in the form and armature of the head in the Cysticercus and Tape-worm, 
had led the earlier ento-zoologists to suspect that there was some latent affinity between 
the Cystic and the Cestoid entozoa, and this surmise has, through recent investigations, 
grown into a consistent doctrine, according to which it is held that the Cysticercus and 
Tmnia are but different conditions of the same animal. It is accordingly now generally 
understood that the ovum, or rather embryo, of a tape-worm, being introduced into the 
body of some higher animal, penetrates through the tissues, probably by aid of the three 
pairs of booklets with which it is armed, and on arriving at a suitable resting-place is 
developed into a Cysticercus^ — in some cases undergoing intermediate changes in its 
progress thither ; that the Cysticercus is destitute of reproductive organs, but that when 
the flesh of the animal which has afforded it a temporary abode is devoured by a second 
animal, the parasite, thus introduced into the alimentary canal of a new host, meets 
with a fitting nidus for further development, and, losing its caudal vesicle, lengthens 
out, acquires transverse articulation, and assumes the form of a jointed tape-worm. The 
term scolex is applied to the cystic, and strohila to the tsenioid form of the entozoon ; 
and, as each articulation of the Tcenia is furnished with a perfect sexual apparatus, and, 
