768 PARASITIC DISEASES. 



have, indeed, contended that there is no such thing as traumatic 

 injury caused by the wandering parasites, but our best experi- 

 mentalists in helmintliology are one and all in favour of the 

 view here advocated. 



Whilst many admirable memoirs have been written on the 

 structure and development of trichina (the literature of the 

 subject being of very great extent), we have on the whole 

 satisfied ourselves that the clearly enunciated statements and 

 conclusions of Leuckart are worthy of every confidence. The 

 following is a brief resume of his conclusions, given almost in 

 his own words : — 



1. TricJiina spiralis is the juvenile state of a little round- worm. 



2. The mature Trichina inhabits the intestinal canal ot 



numerous warm-blooded animals, especially mammals. 



3. The intestinal Tricliince attain sexual maturity on the 



second day after their introduction into the stomach. 



4. The eggs are developed within the parent worm into minute 



filaria-like embryos, which are born free from the sixth 

 day onwards. 



5. The new-born young soon commence wandering, penetrat- 



ing the intestinal walls, and passing directly through the 

 abdominal cavity into the muscles of the host. 



6. The directions in which they proceed are in the course of 



the intermuscular connective tissues, the majority of the 

 embryos resting in the muscles of the abdomen and thorax. 



7. The embryos penetrate the separate muscular bundles, and 



at the expiration of fourteen days they will have acquired 

 the size and organization of the spiral flesh-worm. 



8. Soon after the intrusion of the parasite the infested 



muscular fibre loses its original structure; and after a 

 while the spot occupied by the rolled-up entozoa becomes 

 spindle-shaped, within which the well-known lemon- 

 shaped cysts are formed. 



9. The further development of the muscle tricliinoe is alto- 



gether independent of the formation of these cysts, the 

 walls of which become hardened by calcareous deposition, 

 and thus, moreover, males and females are already dis- 

 tinguishable in the larval state. 



10. The immigration of the young parasites in large numbers 



