n8 Animal Morphology. 



has to be transmitted through joints, and in them we have a 

 ready medium, with a smaller area, to supply with nerve 

 fibres.* 



We now come to the third somatic sense, or the sense 

 apparatus of touch, whose tripartite membrane is the 

 integument. 



This membrane is the most diversified of all membranes 

 in its forms of morphology and modes of cell differentiation. 



It consists of the contractile membrane, in the form of 

 beaded muscle, and dartos ; of a serous membrane, highly 

 modified in the form of hair, scales, nails, claws, feathers, 

 hoofs, etc., according to the special requirements in par- 

 ticular animals, birds, and fish. The basement mem- 

 brane appears to be essentially of that character com- 

 mon to mucous membrane, rather than serous ; and the 

 perspiratory glands and oil glands are essentially of the 

 mucous order, being inflections from the surface, and 

 secreting defined chemical compounds, and here and there 

 most conducive to the well-being of the animal. The serous 

 membrane appears to be in man a kind of arrested and 

 abortive membrane, and which is here called fragmentary. 

 In the subdivision of the animal kingdom, fragmentary con- 

 ditions of membrane are very common, merely serving one 

 particular end, and no trace to be found elsewhere. 



In man it is essentially fragmentary, and also in swine ; but 

 in all instances it is segmented in the highest degree, and 

 then hypertrophied as in hair, feathers, scales, etc. In nails 

 and hoofs it constitutes a terminal segment. Horns belong 

 to the same category, and the spines or quills of the por- 

 cupine and the carapace of the tortoise, the armadillo, and 

 numerous fraternity of the same outward hard casing. The 



* " Upon Nerves distributed to and about Synovial Membrane, as 

 being a Special Seat of Nerves of Force." See Monthly Journal of 

 Medicine, February, 1855, Edinburgh. 



