142 E. PERRONCITO ON THE ENDEMIC DISEASE OF THE 



ON THE LARVAL DEVELOPMENT OF THE ANCHILOSTOMA OR 

 D0CHMIU8 DUODENALIS OUT OF THE HUMAN FRAME. 



The eggs of the Anchilostoma are oval, thin shelled, sometimes so 

 thin as to appear only veiled, of simple form, transparent, the 

 medium longitudinal diameter being 52/z. and the transversal 32^. 

 Cultivated by proper means and necessary heat, they proceed more 

 or less rapidly in their process of segmentation, and thence to the 

 formation of the embryo. Already, after from 12 to 14 hours of 

 incubation, the first larvse are very rarely found ; after a day and a 

 half to two days the greater part of the eggs are open, or present 

 the embryo in different stages of development. 



At the second, third and fourth day of incubation, the number of 

 larvaB always augments in progressive stages. Besides, the matura- 

 tion and hatching of the eggs never happens regularly, and even 

 after many days of incubation embryos are formed, and the hatching 

 of new larv£e effected. 



I frequently saw the larvae make their exit from the shell head 

 first in more or less time, according to the temperature at which I 

 kept the preparations. Keeping the mature eggs at the heat of 

 28 to 33 degs. centigrade, the opening may be seen to occur in two 

 or three motions, which succeed each other in less than a minute. 

 The larva with its head usually opens the Qgg rather laterally from 

 the point ; springs half out, and then with strong lateral move- 

 ments of the whole body holding by the head to the shell of the 

 same egg. The newly-born larvae usually seem torpid ; in some 

 cases they repeat the same motions as when they were enclosed in 

 the shell. Thus, the new larvaB execute movements which may be 

 called automatical, and employ different lengths of time before being 

 able to extend themselves fully. If one observes the embryo through 

 the egg-shell before hatching, one sees it already formed like the 

 newly-disclosed larvas or like those that are two, three, four, or 

 more days old. As soon as hatched the larva is about 200/i. long, 

 and the greatest transversal diameter is 14/x. It presents itself as 

 more slender upwards from the bulb of the pharynx ; it terminates 

 downwards with the tail lessening and awl-shaped. The head is 

 three-lobed and the mouth is represented by a small rectangular tube 

 12yLi. long, which is continued into the pharyngeal canal. The pharynx 

 has an anterior dilatation, which is gradually restricted to form 

 afterwards a fresh globose dilatation, or pharyngeal bulb furnibhed 



