DEVELOPMENT OF MIESCHER's TUBES. 201 



to a more swollen shape, whenever the muscles are loosed from their 

 natural insertion and the fibres contract. 



Their boundary wall consists of a somewhat thick and firm cuticle, 

 which (especially in younger, i.e., smaller tubes) is perforated by 

 numerous pore-canals, of course not always equally distinct (Fig. 105). 

 In consequence of certain external influences, the canals are often 

 united together by rupture, and in such cases the cuticle disintegrates 

 into a fringe of rods, as so often occurs also in the cuticular border of 

 the intestinal epithelial cells. Virchow regards these rods as parts 

 of the surrounding sarcous substance, 1 but in this he is mistaken, as 

 are also those investigators who (with Eainey and Eivolta) regard 

 them as cilia, and make them take part in the movement of the 

 organism. Inside the cuticle, embedded in a tough, somewhat homo- 

 geneous matrix, lie a countless number of microscopic (O'Ol mm.) 

 kidney-shaped or bean-shaped bodies. In their perfectly fresh state 

 these are of a hyaline appearance, containing at most a few sharply 

 defined granules near the ends, and forming- 

 after a while a few vacuoles. Independent 

 movements cannot be observed in those 

 bodies, although they exhibit manifold 

 changes of form. In the younger, i.e., 

 smaller, tubes (of only 07 to 1 mm.), we 

 find, beside and between the kidney-shaped 

 bodies, numerous round transparent balls, 



probably to be regarded as the immature FIG. 105. Extremity of one 

 stages of the former. These structures are $* < ".*% 



not equally Scattered throughout the pro- kidney-shaped bodies, much en- 



toplasm of the tube, but are arranged in lar ecl 



groups, enclosed in thin-skinned spheres of about 0-025 to 0'05 mm., 



which lie together in a closely pressed mass (Fig. 105). 



If, in determining the nature of these structures, we seek to 

 follow the analogy of the other Sporozoa, we may consider the balls 

 as spores, and compare the kidney-shaped bodies with the hyaline 

 rods. 2 The latter would therefore be the embryonic stage. Unfor- 

 tunately we cannot corroborate this plausible hypothesis by positive 

 experimental results. In an experiment which I made, a pig, 

 proved to be free from these tubes, was fed with them, and was 

 afterwards found to be infested with them. But on this I could lay 

 no special emphasis, not only because it was only a single case, but 



1 " Lehre von den Trichinen," p. 23, 1866. 



2 The occasionally slender form of these bodies indeed . recalls the rod-like or sickle- 

 shaped reproductive bodies of other Sporozoa. On the other hand, there are also Fungus- 

 spores of very similar shape. 



