Porocephalus is distinguished from Linguatula by its cylindrical body and by certain internal structures. Porocephalus constrictus is at present only known in its larval stage. It is milk white in colour with golden-yellow hooklets. Number of rings, twenty-three. Length 13 mm., breadth 2·2 mm. There are no prickles on the posterior border of the annulations of the body.
This species was first discovered by Pruner encysted in the livers of two negroes in Cairo. Bilharz reported two further cases in which the parasites were encysted in the liver and in the mucosa of the intestine; a few other observations have been made by Fenger, Aitken, Giard and Chalmas. Aitken’s report deals with soldiers of the British Colonies in Africa. The parasites were discovered in the liver as well as in the lung, and appear to have been the cause of death in one case (pneumonia, peritonitis).
Pruner has found the same parasite also in the liver of the giraffe.
It has recently been assumed that Porocephalus constrictus is the larva of Pentastoma moniliforme, Diesing, 1835, that attains a length of 70 mm. and lives in the lungs of African Pythonides. The larva is known to have been ejected from monkeys (Cercopithecus albogularis, Cynocephalus maimon), from the giraffe (Camelopardalis giraffa), from a species of hyæna (Proteles cristatus), and should be expected to occur frequently in smaller mammals which have been swallowed by African serpents of enormous size.
[The three species of Pentastomidæ, or tongue worms, found in man are Linguatula serrata, Frölich; Porocephalus armillatus, Wyman; and Pentastoma moniliformis, Diesing.
[(1) Linguatula serrata has been referred to under a great number of names.[356] It is a frequent parasite in dogs, oxen and sheep; as an adult in the dog and also in the fox and wolf. The nymphal stage is found in rats, hares, rabbits, the horse, oxen, sheep, goats, pigs, camels, deer, the African and long-eared hedgehogs, porcupine, guinea-pig and peccary. In man it is found in both adult and nymphal stages. Sambon says the nymphal stage is of frequent occurrence, but is usually overlooked. Zenker, who first found it in man, obtained it in nine out of 160 post-mortems, usually encysted in the liver. It is then said to be harmless. Landon, in 1878, found the adult in man, the patient suffering from epistaxis for about seven years; in the end during a fit of sneezing the living parasite was ejected through the nostril. This case is of particular interest as it appears to suggest that this Acarid may now and then pass its entire development in the same host, or at any rate may actively migrate from the liver to the nasal cavities after a period of encystment in the liver or elsewhere, which has also been observed in herbivorous animals (vide also p. [526]).
[It is recorded from man in Central America (Darling, Bull. Soc. Path. exot., 1912, v, p. 118; and again Arch. Int. Med., 1912, v, p. 401), also from Rio de Janeiro (Mem. Inst. Oswaldo Cruz, 1913, fasc. ii, p. 125) by Faria and Travassos.
[(2) Porocephalus armillatus, Wyman, is also known under a variety of names.[357] This species is widely spread over tropical Africa. The adult stage is found in pythons and puff-adders, the nymphal in the chimpanzee, Sykes monkey, mandrill and other monkeys, the lion, leopard, banded ichneumon, Aard wolf, dog, black rat, South African reedbuck and the giraffe. The adult has never been found in man or any mammal. No fewer than sixteen cases of the nymphal form, Sambon tells us, have been found in man, and it is probably much more widespread than at present known. So far it has only been found in the African natives. This species has sixteen to seventeen body rings in the male, eighteen to twenty-two in the female, and the body does not taper as much as in the next species.
[(3) Pentastoma moniliformis, Diesing,[358] is an Oriental species, found in India, Indo-China and South China, and the Malay Archipelago. The adult occurs in both the Indian and reticulated pythons. The nymphal stage has been found in monkeys, the tiger, the civet and the Indian otter.
[The nymph has twice been found in man; in one case in the liver of a Filipino, the other in the serous coat of the small intestine of a native of Sumatra.