SECRETION PHYSIOLOGY. 331 



III. OTHER SECRETIONS DUE TO MUSCLE 



ACTION. 



Probably many other secretions are due to muscle action. 



The unicellular glands of the carp-louse, Argulus foliaceus, 

 are surrounded by muscle fibres. Nussbaum/^ observing the liv- 

 ing glands, states that they are emptied by the contraction of this 

 musculature. Muscle surrounds the unicellular glands in the 

 mantel of Aplysia,'^ and the glandular pedicellaria of the Echino- 

 derms.'^^ The gasteropod liver* possesses, beneath the serosa, 

 an incomplete musculature, the contraction of which has been 

 watched in the living gland. A similar sheath is found in the 

 livers of Crustacea, land and water Isopods, Amphipods and 

 Decapods.'"* 



The poison glands of spiders have their alveoli enclosed in a 

 tunic of spirally arranged muscular fibres.^* In the saliv^ary 

 glands of Cephalopods^^ the cells rest on connective tissue, which 

 is, in turn, surrounded by muscle fibres. An examination of the 

 physiology of these glands leaves little doubt that the secretion is 

 due to muscular action. '^^ The amphibian skin glands are sur- 

 rounded by a muscular sheath lying between the cells and the 

 basement membrane. There is no doubt from observations on 

 the living glands (Engelmann,^^ Drasch,^* Ranvier^^) that this 

 muscle at times contracts, compresses the gland and thus causes 

 a secretion. A similar muscular mechanism prevails in the 

 mucous glands of Petromyzon, in which the cells are bodily 

 extruded. 



The poison glands of amphibia and reptilia and others of the 

 salivary glands"*" are provided with their own musculature, or are 

 emptied by surrounding skeletal muscles. Many anal and 

 cloacal glands,*' sweat^" and sebaceous glands are provided with 

 a musculature lying between the basement membrane and the 

 cells. There is little doubt that the secretion of sebum is pro- 

 duced by the action of this muscle. The same can be said for 

 the secretion of the oil gland of birds. Probably the most in- 

 teresting secretion due to muscular action, outside of the sali- 

 vary glands, is found in the mammalian sweat glands. From 



