328 MATHEWS. 



g. The Location and Nature of the Contractile Substance 



IN the Gland. 



The contractile tissue, responsible for the sympathetic secre- 

 tion, resides neither in the gland capsule nor in the capillaries. 

 Glands dissected free from the capsules secrete normally. The 

 capillaries cannot be held responsible, as Vierheller '^ supposed, 

 because, as one may readily see in the cat's submaxillary, the 

 nerve may be still active on the blood vessels while producing 

 no secretion, and von Wittich"^ records that after curare, the 

 rabbit's sympathetic loses its secretory activity while still active 

 on the blood vessels of the ear. Unna''^ has suggested that the 

 basement membrane is contractile, and this may possibly be the 

 case. There is, however, no evidence of it. That there is 

 smooth muscle about some of the principal ducts of the salivary 

 glands is well-known, but most histologists have failed to find 

 any between or about the alveoli. However, Pfliiger*'" and 

 Schliiter^'' have each described isolated fibres, and strands of 

 smooth muscle lying between the alveoli, distinct from the 

 blood vessels, " so that the stroma is not entirely lacking in 

 contractility." 



Whether the contractile tissues thus far recognized histo- 

 logically in the gland are those active in the production of this 

 secretion appears to be doubtful. The physiological evidence 

 is of itself so strong, however, that I believe we can safely as- 

 sume the existence of such a tissue, even had we no histolog- 

 ical evidence of its presence. 



li. The Changes in Gland Cells upon Sympathetic Stimu- 

 lation. ' 



The changes in gland cells, induced by stimulation of the 

 sympathetic nerve, are most clearly seen in the rabbit's parotid, ^° 

 less clearly in the dog's parotid, where the nerve causes normally 

 little or no secretion. The changes consist in the diminution in 

 the size of the cell, the discharge of the mucous or secretory 

 products, the formation of new undifferentiated protoplasm and 



