DE. T. S. COBBOLD ON TRICHINA SPIRALIS. 211 



distribution legitimately assignable to Trichina spiralis as a good 

 nematode species. Taken in connexion witb what we know 

 touching the limitations of distribution or occupation affecting 

 other species of parasites, the facts have a special and very pecu- 

 liar significance, one, however, upon which I cannot now enlarge. 

 Deducting, therefore, from the 29 experiments the 7 instances, 

 among birds, where the fleshworms would not develop them- 

 selves, and also the three separate cases where the experimental 

 animals escaped, together with one other case where no oppor- 

 tunity of examination was afforded, we have left exactly eighteen 

 mammals in which the results were, in all but two, very carefully 

 ascertained. The exceptions were those of the first two dogs expe- 

 rimented on some two years back. The intestinal caual, or rather 

 its mucous contents, were not sufficiently examined to enable 

 me to affirm positively as to the absence of sexually mature Tri- 

 chinae. In a more recent instance (Exp. No. 23) I had evidence 

 of the difficulty of finding the mature Trichinae in the mucous 

 and half-digested intestinal contents, although the experiment 

 eventually proved perfectly successful. Of course the difficulty 

 of testing the result is a thousandfold increased where only a 

 very small number of Trichinae have been administered. In the 

 sixteen remaining cases the results appeared to have been fully 

 ascertained ; and out of these, nine were perfectly successful. The 

 " negatives " comprised three sheep, two dogs, one pig, and a 

 mouse. The "positives" embraced four dogs, two cats, one pig, 

 one guinea-pig, and a hedgehog. At all events, at least one-half 

 of the experiments on mammals yielded positive results, which, 

 considering all the circumstances of the case, is by no means un- 

 satisfactory. Carnivorous mammals, and especially those which 

 subsist on a mixed diet, appear to be most liable to entertain 

 Trichinae ; nevertheless it is quite possible to rear fleshworms in 

 herbivora. Pagenstecher and Fuchs succeeded in rearing muscle- 

 trichinae in a calf ; and they found three female intestinal trichinae 

 in a goat, but, apparently no muscle-fleshworms, although twenty- 

 seven days had elapsed since the first feeding with trichinized 

 rabbit's flesh. In our three sheep no trace of Trichinae could be 

 found. However, on account of the expense, comparatively few 

 experiments have been made on herbivora ; and therefore, perhaps, 

 it is as well not to speak too positively from the data already 

 afforded. Not that there is really any practical need for further 

 experiments with this species of parasite ; it is quite clear that, in 

 their natural state, herbivorous mammals can seldom have an op- 



