Animal Morphology. 99 



necessary to sustain a complete equipoise between waste 

 and supply ; then the veno-arterial membrane plants reserved 

 stations to act upon emergencies, as a species of temporary 

 scaffolding, or refreshment stalls, which are by no means 

 essential to the well-being of the system, in the form of the 

 vascular glands of Paget, in which vito-chemical changes, 

 and probably certain mechanical advantages, as diverticula, 

 are secured, whereby sudden variations in function, or more 

 chronic conditions of disease, or disturbed function, can be 

 better sustained. 



But we now leave, in a great measure, chemico-vital 

 changes, and those conditions which are essential to secure 

 vital integrity, to consider those higher and more ulterior 

 ends which bring vital force into direct antagonism with 

 the physical conditions by which it is surrounded, by opposing 

 counter-physical and mechanical agencies versus gravitation. 



We begin with the somatic, or body senses more especially 

 the senses of touch, and force or weight, or the muscular 

 sense of Sir C. Bell, and the sense of want, or hunger, which 

 latter has elsewhere been called the hamal sense, and is so 

 closely connected with the ganglionic system in many parts 

 of its distribution as the par vagum, or pneumogastric nerve, 

 which sensory nerve is the first of the somatic senses in 

 the order of appearance in the subvertebrate kingdom.* 



Each sense has superadded to it, its own proper tripartite 

 membrane or sense apparatus, which, for completeness and 

 distinctness, stands in bold contrast to all previous mem- 

 branous mechanism and cell differentiation ; but in its 

 first metamorphic change it approximates in some measure 

 the system of metamorphosis from which it has emerged. 



* " An Experimental Inquiry into the Existence of a Sixth Sense," by 

 R. F. Battye. Vide Edinburgh Monthly Journal of Medicine for Feb- 

 ruary, March, and April, 1855, and Edinburgh Medical Journal for 

 February, March, and May, 1859. 



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