94 ANATOMY AND PHYSIOLOGY 



sarcode lining the interior of the sponge and the so-termed 

 mucous lining of the intestines of the higher animals. 

 Under natural circumstances the two substances are in- 

 soluble in water, but under the effects of certain stimuli 

 they are each discharged from their natural bases with 

 great facility ; and where this discharge prevails to any 

 great extent, it appears to be speedily fatal to the life of 

 the animal. Thus in cases of extreme diarrhoea in warm- 

 blooded animals, immediate prostration of the vital powers 

 is the inevitable result ; the final and most important act 

 in the sustentation of the vital powers is greatly interfered 

 with or entirely destroyed, and great prostration of strength 

 or death is speedily the result. The marine Spongiadaa, 

 under ordinary circumstances, may be kept in their natural 

 element, and death may ensue for want of a supply of fresh 

 water, without any remarkable amount of viscous dis- 

 charge. But if we remove a living specimen of Halichon- 

 dria panicea from salt water and plunge it into fresh water, 

 the result is frequently an immediate and profuse discharge 

 of a glairy gelatinoid matter. The same result may be 

 induced by an addition of a considerable quantity of salt to 

 the sea water in which the animal was contained, or by the 

 addition of a small portion of alum ; and when once this 

 viscous discharge has been induced, the life of the sponge is 

 inevitably destroyed. In others of the lower marine 

 animals the same effect is induced by similar causes, and 

 with many of them the immersion in fresh water is noto- 

 riously the quickest and most certain mode of destroying 

 vitality, and in these cases the decease is almost always 

 accompanied by an abundant flow of viscous matter. 

 Thus if we have this substance upward from ActynopJirys 

 Sol to man, through the Spongiadse and all its other gra- 

 dations of animal existence, it is always found to be pre- 

 sent, and always intimately connected with the digestive 

 process. Especial organs for respiration, nerves for sensa- 

 tion, muscles for motion ; all these may apparently be 

 dispensed with in turn, and yet the animal will perform its 

 accustomed functions ; but this substance, as mucous lining 

 of intestine, or sarcode, as I have before observed, appears 



