430 



TEGUMENTARY ORGANS 



In Fishes and Reptiles the superficial layer of striped muscles of 

 the body is always more or less connected with the integument ; but 

 hitherto no unstriped fibres appear to have been detected in it. In 

 Birds, however, the unstriped muscles attain a very great development,, 

 forming a thick layer whose bundles (<:) run between and are attached 

 to the sacs of the feathers {fig. 322). 



In the majority of Mammals there is a special tegumentary striped 

 muscle; which attains an enormous development in the hedgehog,, 



while a mere rudiment of it remains 

 in man, as the platysma myoides- 

 Here, however, the striped " pean- 

 cier " muscle is replaced by the 

 unstriped bundles which, as Kolliker 

 has shown, run from the upper layer 

 of the enderon to the bases of the 

 hair sacs, and effect the various 

 movements of which the hairs are 

 capable. 



Calcareoits deposits in the enderon.. 

 — Deposits of this kind are very 

 frequent in the Invertebrata. In the 

 Pulmonate and some Gasteropod 

 Molluscs, for instance, globular 

 masses of carbonate of lime are 

 scattered through the enderon, and 

 would almost seem to take the 

 place of fat. In nudibranchiate mol- 

 lusks, such as the Dorida, spicula of 

 like nature are met with, and these sometimes unite into true internal 

 shells, as in the genus Villiersia. The greater part of the skeleton of 

 the Actinoid polypes, and the whole of that of the Ecinoderms, is 

 composed of calcareous networks of this kind, and globular masses of 

 calcareous matter are scattered through the enderon of the Tseniadae, 

 though the clear spherical bodies observed in these worms are by no 

 means always of this nature. Whether these enderonic calcareous 

 deposits ever take place in the Vertebrata appears to me to be, as I 

 have said above, an open question, only to be decided by a very 

 careful examination of the mode of growth of their so-called "dermal"' 

 bones. 



Bibliography. — General Works. — Heusinger, Histologic. Quekett, Lectures on His- 

 tology. 



Vertebrata. — Gurll, Untersuchungen Uber die hornigen Gebilde d. Menschen u. d.. 



Fig. 322. — Pacinian body (i5) and feather- 

 sac {a) from the base of the mandible 

 of a pigeon, c, muscles of the feather 

 sacs. 



