428 REPORT OF THE HARVARD AFRICAN EXPEDITION 
these parasites than has man. Filleborn and Kikuth ! have recently considered 
the immunity and cutaneous immune reactions in helminthic infections. While 
in a few instances of infestation with animal parasites the modification of the 
blood of the host is of such a nature that the resulting immunity can be demon- 
strated by serum reactions, as in the case of some bacterial infections, in more 
instances of parasitic infection no such immunity can be demonstrated sero- 
logically. Nevertheless, it appears that species or races of animals which have 
harbored a given parasite for a long period of time usually show less marked 
effects of the result of its presence than species that previously have not been 
subjected to such infestation. Sandground ? has recently discussed the factors 
of age resistance and acquired immunity in helminthic infections of animals, as 
well as the nature of the immunity or resistance acquired in certain instances. 
He points out that while a very plausible explanation for the age resistance can 
be formulated on natural grounds, the elaboration of a hypothesis to account 
for acquired immunity is much more difficult. Although an animal may acquire 
an immunity to a specifically normal parasite, as might be expected, the ten- 
dency to do this is greater when the species of parasite involved is one in which 
the host does not have an autochthonous relationship. However, that many 
animals acquire a definite resistance against certain parasitic infections would 
appear to be unquestionable. Stunkard,’ also, has recently given much evidence 
of this fact. 
The more important parasites of wild game, regarding which observations 
were carried out by us in Africa will now be discussed. 
Hyena (Crocuta crocuta thomasi). We expected to find animal parasites in 
the hyena owing especially to the fact that it preys largely upon dying and dead 
animals. ‘Trypanosomes have been found previously in the hyenas in districts 
where sleeping sickness is prevalent, and they have been known to carry off and 
devour the dying sleeping sickness victims from the sleeping sickness camps and 
lazarettos in some districts in East Africa.4/ We, however, found no trypanosomes 
in the four hyenas that were examined nor did we find any evidence of animal 
parasitic infections in them, though special examinations were made of the 
spleen, blood, and intestinal tract. 
Neveu-Lemaire ° in his article upon the mammals which may serve as the 
reservoirs for the virus of infectious diseases and for parasites of man only men- 
tions the hyena as a host of the trypanosome of nagana and of the virus of rabies, 
and refers to the observation of Southwell that it may be a host of Dipylidium 
caninum. Fantham, Stephens and Theobald ° note the occurrence of the larva 
of Porocephalus constrictus in the earthwolf Proteles cristatus, which, however, 
they have erroneously referred to as a species of hyena. 
In one of our hyenas there was a wart-like tumor near the vagina measuring 
' Fiilleborn and Kikuth:. Beihefte, Arch. f. Schiffs-u. Tropen-Hyg. (1929), XX XIII, 168. 
2 Sandground: Parasitology (1929), X XI, 227. 
3 Stunkard: Scientific Monthly (1929), XXVIII, 349. 
4 Roosevelt and Heller: ‘‘ Life Histories of African Game Animals” (1914), I, 259. 
5 Neveu-Lemaire: Ann. de Parasit. (1927), V, 254, 378. 
6 Fantham, Stephens and Theobald: “The Animal Parasites of Man” (1916), Doves 
