ANIMAJ PARASITES. 141 



scesses and ulcers. The embryos live for a time free in fresh water, and 

 are then taken up by a species of fresh- water crustacean, in whose body 

 they undergo further development, and by the ingestiou of which the 

 infection of the human subject occurs. 



Filaria sanguinis hominis. The embryo of this parasite, which inhabits 

 the blood and lymph of man, especially in Brazil, Egypt, and some parts 



of the Orient, and occasionally occurs 

 i n this country, is about 0.35 mm. 



//w long ' rouu(ie<i anteriorly, and pointed 



\{M at the tail (Fig. 68). It has about 



>t6 -** the diameter of a red blood cell. It 



^'"~^*^^* ^curs, sometimes in great numbers, 



in the blood during the night time, 



being as a rule absent during the day. It may occur in the urine in 

 connection with chyluria and hsematuria. The mature female is from 

 8 to 10 cm. long, and has been found inhabiting the lymph vessels of 

 man, particularly in the scrotum and lower extremities. Owing to the 

 obstructions which it causes in the lymph circulation, and to the local 

 irritation which its presence induces, it sometimes give rise to lymph - 

 angiectasis, 1 oedema, abscesses, and perhaps elephantiasis. One of the 

 embryonic stages of development is believed to take place in the body 

 of a species of nocturnal mosquito. Through the bodies of the dead 

 mosquitoes, which are liable to fall into the drinking-water, it is believed 

 that the spread of the parasite may occur. 



There are several other species of filaria occasionally found in man 

 which it is not necessary to enumerate here.* 



Rhabdonema strong t/loides. A small, filiform worm from 1 to 2 mm. 

 in length is found, often in enormous numbers, in the intestines, biliary 

 and pancreatic ducts of man in Cochin China and in Italy, giving rise to 

 endemic diarrhoea. It has been thought that there are at least two 

 species, which have been described under the generic name Aguillula, but 

 recent researches by Leuckart have led him to believe them to be differ- 

 ent developmental stages of the same form, for which he suggests the 

 above name. 



Methods of Study of Worms. 



Filaria sanguinis may be preserved by preparing a smear of the blood containing 

 it on a slide in the usual way (see p. 882), and staining with methylene blue. 



The larger parasites may be hardened in formalin and studied whole after dehydra- 

 tion in alcohol and clearing in oil of cedar or origanum. Or sections may be made after 

 embedding, and stained and mounted in the usual way. 



The examination of muscle for trichina is often of great practical importance. For 

 this purpose small pieces of fresh muscle are squeezed into a thin sheet between two 

 slides, and examined with a low power, A considerable number of bits of muscle should 

 be examined, particularly from the above-mentioned favorite situations, before exclud- 

 ing them in a suspected case, because they are sometimes present in small numbers. A 

 thorough search is of special importance in the examination of pork, since, owing to 



1 For a study of filarial lymphatic vanx see Ojn'e, Trans. Assn. Am. Phys., vol. xvi., 

 p. 314 



''For bibliography consult htthrop a ml Pratt, Am. Jour. Med. Sciences, vol. cxx., 

 p 525, 1900 



