NEMATODA, THREAD-WORMS 555 



The young embryos have a length of 0.1 mm., a breadth of 0.006 mm. The 

 anterior end of the body is thicker than the posterior. After entering the mus- 

 cle, they penetrate still more deeply into its interstitial tissue, in a longi- 

 tudinal direction, toward the insertions of the tendons. Their path through 

 the fibers causes a number of changes in them. The trichina has a destructive 

 action upon the finer constituents of the fibers. These lose their transverse 

 striae and are changed into a fine granular mass. Without doubt the embryo 

 is nourished by the decomposed muscular substance. I do not wish to be 

 wearisome with the finer histologic details, and shall emphasize only the fol- 

 lowing points in the development of the muscle trichina: The development 

 occurs in about fourteen days. The muscle trichina gradually grows to a 

 length of 0.12-0.16 mm., simultaneously rolling itself into a spiral. The 

 sarcolemma distributes itself about the embryo, and thickens. In the inter- 

 stitial tissue, as well as in the muscular substance, such an increase of the mus- 

 cle nuclei occurs that the trichina appears completely embedded in them, and 

 surrounding it is an areola of granular material which stains more intensely 

 than the remaining contents of the nodule. After about four weeks the con- 

 tents of the nodule permeated by nuclei enter upon a process of reconstruction, 

 which, beginning at both ends, rapidly reduces these ends to thin threads. 

 Around the spiral swelling, as well as around the threads, is a gelatinous 

 sheath which Leuekart recognized as thickened sarcolemma. Outside of this 

 is a zone of inflammatory connective tissue richly supplied with connective 

 tissue corpuscles and leukocytes. Later the disorganized muscular mass in 

 the region of the thread-like processes disappears. The connection with the 

 material surrounding the trichina is interrupted. The formation of a clearly 

 defined trichina capsule now begins; starting from the surrounding con- 

 nective tissue cells, probably in the course of the old gelatinous sheath, the 

 new and firmer cyst is separated from the encroaching connective tissue cells. 

 Fat cells develop at the poles of the capsules. At about the sixth month the 

 capsule begins to calcify owing to a deposit of calcium carbonate. This cal- 

 cification may also affect the enclosed trichina. According to Langerhans, the 

 trichinae as well as their capsules are capable of retrogression and may 

 finally, although only after many years, be completely eliminated from 

 the body. 



In man, the source of infection is almost exclusively the pig, very rarely 

 the wild boar and the bear. The danger of transmission of trichinae capable 

 of development from the ingestion of infected pork depends upon the prepara- 

 tion of the meat. People who partake of infected pork raw or insufficiently 

 cooked show the most severe symptoms. Eaw meat in the form of so-called 

 hash, boiled fresh pork from a newly killed pig, roast sausage or German 

 sausage (Knackwurst) in the preparation of which the heating is insufficient 

 to insure the destruction of the trichina appear to be especially dangerous. 

 The ingestion of meat of this kind, which is particularly common in Middle 

 and North Germany, causes the frequent appearance of the disease in endemics 

 and epidemics. In the sixth decade of the last century severe epidemics of this 

 kind were observed in Plauen, Hettstadt, Hedersleben. In South Germany, 

 and in other countries, France, England, Belgium, America, etc., this custom 



