Animal Morphology. 105 



membrane is isolated by origin and insertion, as so many 

 segmentations, under the title of muscles. 



As. of the sense apparatus of the haemal sense, so also of 

 the sense apparatus of the sense of force ; it is essentially 

 segmental in the contractile membrane. Whilst all the 

 membranes of animal life are essentially segmental, that 

 of the serous membrane is pre-eminently so in the sense of 

 touch. But of that more by-and-bye. To express the same 

 view in another form instead of a continuous membrane, 

 the same membrane is repeated over and over again in 

 completing any proper or special membrane. 



To give a simile of a quadruple membrane may perhaps 

 assist our understanding of the engrafting of the senses, on 

 leaving the brain and spinal cord, as being a part of a special 

 membrane external to the brain, and henceforth incorporated 

 with the functions and working of a distinct apparatus, 

 whilst in its major function it is debtor to the brain 

 itself. 



Let a gasometer stand for the brain ; the main pipes and 

 service pipes for the spinal cord and roots of nerves. 

 But from the house meter and within, all gas apparatus 

 and piping inside the house is bought and sold with the 

 house ; but though the proprietary is distinct, yet all burners 

 in a house are more dependent upon the supply from the 

 gasometer forty yards off, or one or two miles, than they 

 are for any supply they get as the result of gas-fittings 

 within the house. This is a rough simile, but it may serve 

 to illustrate what is meant by the senses in their ultimate 

 distribution outside the brain and spinal cord ; when 

 external to these centres each sense has its own tripartite 

 membrane, as each house has its own gas-fittings distinct 

 from the gas-works. 



We now go on to consider the haemal sense, or parvagum, 

 alias the sense of want ; as hunger, etc., it occupies its proper 



