19, 3 Maxwell: Filariasis in China 261 
of the mosquito, apparently with a view of leaving the mosquito 
when it bites, and this migration generally takes place in pairs. 
The parent filariz * have been found many times. They are 
nematode worms, both sexes being found in the human body 
“often inextricably coiled about one another.” They are some 
3 to 4 inches (7.6 to 10.2 centimeters) in length, hairlike, and 
transparent. They have been found in many situations: in 
lymphatic trunks, in lymphatic varices, in varicose lymph glands, 
in the tissues removed in operating on lymph scrotum, in the 
tissues removed in operating on elephantiasis of the scrotum, 
and in filarial abscesses. The female worm is the larger of 
the two. In length, it is from 3 to 4 inches (7.6 to 10.2 cen- 
timeters) ; in breadth, about 1/90 of an inch (0.2 millimeter) ; 
the greater part of the body is occupied by the two uterine 
tubes, containing ova in all stages of development. The head 
is club-shaped and simple, and the tail is tapered and rounded 
off, with the anus opening just in front of its termination. The 
vagina opens near the mouth. The cuticle is smooth and devoid 
of markings. 
The male worm is very slender and has a marked tendency 
to curl. The extreme end of the tail is sharply incurved. The 
cloaca gives exit to two unequal, slender spicules. Caudal pa- 
pill are present. These parent filarie have considerable mo- 
bility and can be kept alive in salt solution for some hours. 
Having described the parental forms of the worm, let us look 
at the characters of their progeny. 
The ova are not normally found in the blood or lymphatic 
system; in fact, the appearance of these probably means that 
parturition has not gone on normally and has an important 
bearing on the question of lymphatic obstruction. I have met 
with them once in a case of lymph scrotum, in a microscopic 
preparation got by tapping the lymphatic system of that part, 
and in this case repeated examination failed to find the embryo 
in the blood. On the other hand, the embryo could be readily 
made out coiled up inside the ovum. The size of these ova 
is stated by Manson(25) to be about 1/500 by 1/750 of an inch 
(0.051 by 0.034 millimeter). The embryo coiled up in the ovum 
gradually stretches its chorional envelope, which probably forms 
the sheath of the mature filarial embryo. 
In describing the embryos of Filaria bancrofti, as commonly 
met with in the blood, I largely follow Manson’s description, 
*For a full description of the parent filarie and their embryos see 
Tropical Diseases. Cassell, London (1917) 681-702. 
