484 EDWIN S. GOODRICH. 



Camera drawings on a large scale were, therefore, made ; 

 then combined by means of transparent tracing paper, the 

 communications of the capillaries being verified in every case 

 with the greatest care under the high power. 



Before describing these important capillary systems, in 

 which the communication really takes place, it is necessary to 

 give an account of the large vessels and sinuses, in order to 

 show that amongst these there is no continuity of the two 

 systems. 



The Lateral Vessels and their Branches. — A large 

 longitudinal vessel, with muscular contractile walls, extends 

 in a sinuous course along each side of the body. This is the 

 well-known lateral vessel, and is said to communicate in 

 front and behind with the corresponding vessel of the opposite 

 side. In every segment the lateral vessel gives oflF a pair of 

 large dorsal branches (figs. 1, 2, 6). The first of these is the 

 short latero-la teral vessel of Gratiolet, passing almost 

 vertically upwards to break up into smaller branches, and lead 

 to the superficial cutaneous capillary network on the dorsal 

 and lateral regions of the body. 



The second is the more important latero-dorsal vessel of 

 Duges. This vessel soon divides into two large branches, the 

 anterior of which passes over to the opposite side to join its 

 fellow above the dorsal sinus, and the other, the posterior, runs 

 towards the median line, but does not communicate with the 

 vessels of the opposite side. Both these branches give off smaller 

 vessels running outwards to the superficial capillary networks. 



The anterior branch of the latero-dorsal vessel also gives off 

 vessels passing downwards to the wall of the gut. 



The entrance of the large, and contractile, latero-lateral 

 and latero-dorsal vessels into the lateral longitudinal vessel is 



possible to avoid all sorts of errors on superimposing the camera drawings. 

 The slightest inaccuracy in such drawings — due, for instance, to the somewhat 

 different position of the eye in making them, or jjcrhaps to a slight shrinking 

 or expansion of the section itself — would be sufficient to vitiate the whole 

 result by leading any given capillary to wrongly fit on to any of its nearest 

 neighbours. 



