241 



stomach juices, and the contained scolex, or head, is then free 

 to attach itself to the mucous membrane and to grow into 

 maturity. The ova of T. solium are round, with a striated 

 double-contoured envelope. They measure from 40-50 /j. in 

 diameter. The ova of the T. saginata are larger and coarser. 

 They are both of a brown color and dense appearance. The 

 ova of bothriocephalus are somewhat larger and more oval ; 

 the envelope is thinner. 



A form of tsenia, fortunately very rare in the United States, 

 but more common in countries in which the association with 

 dogs is common, especially in such countries as Iceland, where 

 the transportation problem is settled by the employment of 

 dogs, and where, on account of the cold, very often dogs and 

 men are huddled together, the Tsenia echinococcus very often 

 causes serious results. It is a parasite of the intestinal canal 

 of dogs principally. The adult worm consists of a head and 

 three segments. It measures in length 4 to 5 m.rn. The head 

 has four sucking disks and a double row of booklets. The 

 eggs are numerous, and when sw r allowed the larvaB are liber- 

 ated and burrow into the liver, spleen, muscles, and other 

 parts of the body. Here they develop into cysts with clear 

 contents (hydatids). These cysts increase in size and develop- 

 ment by a system of interior projection or budding which is 

 continuous, daughter and granddaughter cells being formed. 

 From the inner granular lining of these daughter and grand- 

 daughter cells broad capsules are developed. From the lining 

 of these latter, scolices with sucking disks are formed. These, 

 when ingested by a dog or man, may develop into tsenia. 

 Sometimes these cysts rupture. The fluid contained in them 

 is non-albuminous in character, an important point when aspi- 

 ration has been done for diagnosis, and may contain booklets. 

 In echinococcus cyst of the kidney booklets may appear in 

 the urine. The sputum may show booklets in echinococcus 

 cyst of the lung. 



TRICHINA. 



A species of worm which causes considerable illness and 

 fatality, less so now than formerly, is the Trichina spiralis. 

 16-M. B. 



