Microscopical Society. 1361 



ring only in certain portions of the torrid and north temperate zones, 

 in Africa and Asia. It is especially frequent on the coast of Africa, 

 and thence derives its vulgar name of Guinea Worm. Together with 

 this limited general range, it is also known that the disease caused by 

 the worm has been sometimes observed to be periodical, and appa- 

 rently connected with change of the seasons. And it is also known 

 that however prevalent, or even general the worm may. be in one place, 

 for instance, on the coast of Africa, it will not be found in another 

 only a few leagues distant. No restriction of intercourse at the same 

 time existing between the two places. Notwithstanding this limita- 

 tion in the range of the Filaria, no race of mankind is exempt from 

 its attacks when exposed to what may be termed the contagion 

 in those places where it is epidemic. But though carried about the 

 world in this way, no instance of its spreading in any other countries 

 than those indicated is known, unless it be a doubtful one in the Is- 

 land of CaraQoa. The deduction drawn from these facts, is that the 

 Filaria Medinensis requires for its successful propagation certain con- 

 ditions of nature external to the bodies inhabited by it. 



The structure of the worm was described. When perfect, its ave- 

 rage length is from four to six feet, and it presents a head or oral ex- 

 tremity, and a posterior or caudal extremity. The oral extremity is 

 not frequently met with, owing to the circumstance that the worm in- 

 variably presents itself at the surface with that end first, which conse- 

 quently is generally rubbed or pulled off before the case can come 

 under observation. It appears, however, that this extremity is blunt 

 and rounded, and furnished with a minute circular oval aperture, 

 around which the integument is thrown into radiating folds. The 

 body of the worm is cylindrical, and of uniform size, or nearly so 

 throughout, and it terminates posteriorly in a pointed, and more or less 

 acuminate extremity, which is also always more or less incurved. The 

 difference in the degree of acumination and curvature are consider- 

 able in different individuals, and so much so, that the varieties have 

 been elevated into marks of sexual distinction. An error, at one time 

 adopted by Rudolphi, but which he afterwards abandoned. It is evi- 

 dent that no real ground for making a distinction from such a charac- 

 ter is tenable, for the reason, that worms of every variety of tail will be 

 found to contain young ones, and must consequently be held to be all 

 of one sex. There is no anal or other opening visible at the caudal 

 extremity of the worm, nor in any part of its length. 



The worm is composed of an outer integument, and of an internal 

 tubular cavity. 



IV 5 E 



