XXXVIII 



TEGUMENTARY ORGANS 



The Cyclopcedia of Anatomy and Physiology, edited by Robert JJ^. 

 Todd, M.D., F.R.S 



The fascicules containing this article were published between August, 1855, 

 and October, 1856 



In endeavouring to deal with so large a subject as the tegumentary 

 organs of animals, within the limits of an article like the present, it. 

 appeared advisable not to attempt to enter into minutiae of detail 

 (which indeed fall more properly within the province of those who. 

 treat of the special classes), but so far as possible to regard these 

 organs as a system in the sense of Bichat — as a sort of zoological class 

 — whose members, the tegumentary organs of particular animals, are 

 but special modifications of one general plan. In reflecting how this 

 might best be done, however, I was met at the outset by certain 

 difficulties and perplexities whose solution appears to me to be- 

 essential to any philosophical treatment of the subject, and to the 

 consideration of which I, therefore, propose to devote the following 

 Preliminary Section. 



§ I. My first difficulty was to find an answer to the question, — What 

 constitutes a tegumentary organ as distinguished from any other ? 



The most obvious definition of an integument or tegumentary organ 

 is, of course, — that which forms the external covering of any animal — 

 viscus, on the other hand, being that which is contained. More 

 strictly, it may be said that the integument constitutes that free 

 surface of an animal which is external to the edges of the oral and anal 

 apertures, or where the former alone exists, to its edge. Now these 

 definitions are perfectly sufficient so far as surface is concerned ; but 

 suppose we make a section perpendicular to the surface, where does 

 integument cease, and where does viscus begin? So far as I am 



