Physiology of Hsematopinus tenuirostris, Burm. 103 



unite with the motor of the tarsus (fig. 6,/ 1 ). The flexor 

 tarsi has a triple origin. Its principal portion originates in 

 the sinuosity of the tibia which is directed backwards, and 

 runs forwards thence, gradually becoming narrower (fig. 6, a) ; 

 a second part is inserted upon the anterior basal margin of 

 the tibia (fig. 6, 6), unites, after a short course, with the 

 muscle (f l ) coming from the femur, and both combine with 

 the principal part after they have become considerably nar- 

 rowed. At its extremity the flexor of the tarsus passes into 

 a fine clear sinew (fig. 6, ft). The latter is attached to a 

 finely ribbed chitinous plate (r/), which is connected with the 

 claw of the tarsus. If then the flexor tarsi contracts, the claw 

 is approximated to the chitinous process (e) on the anterior 

 margin of the tibia, by which means the animal is able to 

 clasp the hairs of its host. 



There are several muscles which serve for the constriction 

 of the thorax. The first of these originates above the muscles 

 which run to the first pair of legs, and is inserted upon the 

 anterior margin of the first acetabulum on each side (fig. 4, x). 

 The second is inserted between the muscular fasciculi which 

 run to the first and second pairs of legs, and terminates be- 

 tween the first and second acetabula (fig. 4, z). The third 

 originates between the muscles going to the second and third 

 pairs of legs, and terminates between the middle and posterior 

 acetabula (fig. 4, y). Besides these there is yet a fourth 

 strong muscular bundle, which serves the same purpose. 

 This, w T hich forms a broad band adhering to the dorsal in- 

 tegument, runs from one side to the other at the hinder mar- 

 gin of the thorax (fig. 4, t). By the contraction of all these 

 muscles, or of a portion of them, the dorsal integument of the 

 thorax is approximated to the ventral. 



Three of these pairs of muscles effect the movement of the 

 head. One of them originates on the chitinous pad at the 

 point where this divides, and runs forward to the lateral mar- 

 gin of the head (fig. 4, r) . The second is inserted above the 

 fork of the chitinous band, and runs perpendicularly to the 

 boundary of the first and second acetabula (fig. 4, q), where 

 it meets with the third pair, which commences at the lateral 

 margin of the head, and thence goes obliquely downwards 

 (fig. 4, p). All these muscles serve to move the head side- 

 ways and downwards. I have been unable to discover any 

 special upward motors of the head, and therefore assume that 

 the chitinous fork which has been repeatedly mentioned acts 

 at the same time as an elastic band which draws the head 

 upwards. 



Musculature of the Abdomen. — As in the case of the 



