TMNIA. 



77 



Fig. 23. 



■digestive system and bloodvessels are absent, but in the inner 

 layer we find a system of very much branched vessels which 

 connect with two elongated canals united at each joint by a cross 

 system of similar canals, which is said to serve as an excretory 

 apparatus. The branches running into these canals end in a 

 common orifice. Each link or segment 

 has an independent male and female 

 sexual apparatus. The male apparatus 

 consists of numerous pear-shaped testi- 

 cular bladders with a canal of exit. The 

 end can be turned up into the female 

 opening. In the female portion we can 

 distinguish ovaries, uterus, and vagina. 

 The uterus is remarkably well defined 

 in each segment. 



The following varieties are seen in 

 the dog : 



Tsenia Serrata. This variety is from 

 €.5 to 1 m. in length and about 0.5 cm. 

 in width when fully developed. The 

 head is large proportionately, often four- 

 sided, and is fitted with two rows of hooks and also sucking disks, 

 which are oval in shape. The anterior border of the segments 

 is much narrower than the posterior. The 

 edges are serrated or saw-like, hence the name. 

 The genital orifice is situated on the border, 

 sometimes on the right and sometimes on the 

 left. The full grown segments are nearly square, 

 or may be broader than long. The uterus has 

 a large central body, with eight branches on 

 each side. The eggs are indented on the sides 

 and have a hard, tough shell. The bladder- 

 worm is found in the liver of the hare, called 

 cysticercus pisiformis. This club-shaped cyst, 

 which is from 8 to 13 mm. in length and 4 to 

 6 mm. in width, has been found by Lesbre in 

 the brain of a dog affected by tsenia serrata. This was probably 

 caused by self-infection. 



Taenia Marginata. This is the largest tsenia of the dog, being 



Taenia serrata ; a u u, natural 

 size ; ft, egg, greatly magnified. 



Taenia marginata 

 (natural size). 



