570 THE ANIMAL PARASITES OF MAN 



is still debated. This acarus lives in the hair follicles in comedones and in 

 the glands of Meibomius in the skin of the face of man. In the dog, the pig, 

 the cat, and in cattle, hair follicle acari have been observed and are said to be 

 varieties of the parasite of man. The views of authors are divided as to the 

 importance of this parasite as a causative agent of disease. We incline more 

 and more to the opinion that it is one of the harmless parasites, and that its 

 occurrence in acne pustules is of no pathogenic significance. Nevertheless, 

 it is found with extraordinary frequency — according to Hunsche even in 92.5 

 per cent. — in the sebaceous glands of perfectly healthy individuals. The clin- 

 ical conception formulated by Eaelmann of blepharitis acarica can no longer 

 be maintained. The acarus is found with great regularity in the ciliary folli- 

 cles of normal, as well as of abnormal, eyelids. 



Of the linguatula, or tongue worms, which are elongated, vermiform, flat- 

 tened or cylindrically curled worms whose head is armed with an elliptical 

 chitin mouth and two retractile claws, one is parasitic in man. This is the 



Pentastoma tcenioides, Rudolphi, 1810. 



The sexually mature parasite lives in the nasal cavity, the forehead bones 

 and Jaw of the dog, the wolf, the horse, the mule, the goat, and, occasionally, also 

 in man. The eggs discharged with the nasal mucus contain embryos which 

 reach the open air where they are taken up by such animals as rabbits, hares, 

 cattle, horses, etc., and also sometimes by man. They penetrate the intestinal 

 wall, and reach the liver where they become encysted. For a long time the 

 larva pentastoma denticulatum, Eudolphi, was taken for an independent para- 

 site. After a certain time the larvse may wander further, and in this way 

 reach the respiratory tract, especially the nose. In other cases infected organs 

 are eaten by carnivora. The larva which reach the intestinal tract finally 

 find their way to their preferred points of lodgment. Man unquestionably 

 infects himself in a similar manner. The pentastoma either accidentally 

 reaches the nose or is introduced into the intestinal canal by contaminated 

 food. 



The sexually mature form is rarely met with in man. Laudon found the 

 parasite in a locksmith, who suffered for years from jaundice and gastric dis- 

 turbance, and later from epistaxis. Usually the larva (the pentastoma den- 

 ticulatum), when observed in man, is found particularly in the liver, the lung, 

 the spleen and small intestine, the peritoneum, the heart muscle and the 

 kidneys. Special symptoms are not present in these cases. The pentas- 

 toma can be diagnosticated only when they give rise to irritative symptoms 

 m the nose or its auxiliary cavities or when their ova are found in the 

 nasal secretion. 



Pruner was the first to find in the liver of two negroes the 



Pentastoma constrictum, v. Siehold, 1852. 



Observations regarding the occurrence of this parasite are very scanty. 

 It appears that when present in great numbers it may be the cause of fatal 

 peritonitis. 



