ANIMAL PARASITES AND MESSMATES. 677 



kidneys. As a rule, those which inhabit a temporary host install 

 themselves in a closed organ ; in the muscles, the heart, or the lobes 

 of the brain ; those, on the contrary, which have arrived at their des- 

 tination, and which, unlike the preceding, have a family, occupy the 

 stomach, with its dependencies the digestive passages, the lungs, the 

 nasal foss*, the kidneys, in a word, all the organs which are in direct 

 commimication with the exterior, in order to leave a place of issue for 

 their progeny. 



A single animal may carry, not only a great number of individuals 

 of the same species, but many different species of parasites, and this, 

 too, without any apparent impairment of health. Indeed, in some coun- 

 tries their presence is considered indispensable to the highest health, 

 the Abyssiniaiis, for example, deeming themselves below par unless 

 they nourish one or many tapeworms. Nathusius speaks of a black 

 stork which lodged 24 Filarice in its lungs, 16 Syngami tracheales in 

 its tracheal artery, more than 100 Spiropteroe within the membranes 

 of the stomach, several hundred of the Holostomiim excavatum in the 

 smaller intestines, 100 of the Distoma ferox in the large intestines, 

 22 of the Distoma Mans in the oesophagus, and a Distoma echinatum. 

 in the small intestine. In spite of this affluence of lodgers, the bird 

 did not appear to be the least inconvenienced. Krause, of Belgrade, 

 mentions a colt, two years old, which contained more than 500 As- 

 carides, 190 Oxyures, 214 Strongyli armati, several million Strongyli 

 tetracanthi, 69 Tceiiia, 287 Filarice, and 6 Cysticerci. Well supplied 

 as these animals appear to have been, when we consider the number 

 of eggs a single worm may produce, the wonder is that parasites are 

 not more numerous than they are : 60,000,000 eggs have been counted 

 in a single nematode, and in a single tapeworm more than 1,000,000,000 

 eggs have been found ! 



While nearly all animals, including parasites themselves, are made 

 to contribute to the support of others, those to which man gives food 

 and lodging are of greatest interest, and he is by no means scantily 

 provided with this class of dependents. Four different cestodes, or 

 tapeworms, live in his intestines ; three or four Distoma lodge in his 

 liver, intestines, or blood ; nine or ten hematodes, or round worms, in- 

 habit his digestive passages or flesh ; and cysticerci, echinococci, and 

 hydatids, are also among his guests. He provides a living for three 

 or four kinds of lice, for a bug, for* a flea, and two ascarides, without 

 mentioninsc certain inferior organisms which lurk in the tartar of the 

 teeth, or in the secretions of the raucous membrane of the mouth. 

 Some of these are confined to him exclusively, others may also find a 

 home on the lower mammalia ; some make his body their home while 

 passing through a single stage of development, beginning or finishing 

 the process, as the case may be, in the body of another animal ; and 

 others, again, are but day-boarders, taking their meals at his expense, 

 and finding lodgings elsewhere. 



