THE RELATIONS BETWEEN THE ENDOCRIN ORGANS 179 



anemias resulting from irritation and by the presence of pronounced 

 dermographism. This author states that the injection of epinephrin pro- 

 duces an abnormal sympathetic reaction, as shown in the blood pressure, 

 heart action, and contraction of vessels of the skin ; also an abnormal para- 

 sympathetic reaction on the injection of pilocarpin, shown by profuse 

 sweats, salivation, increase in flow of tears, hypersecretion of the gastro- 

 intestinal tract, nausea, vomiting, and diarrhea. 



The opinion seems to be generally accepted that the reduction in the 

 calcium content of the blood increases the excitability of all nerve centers, 

 both those of the central and vegetative systems. 



The Thymus and the Autonomic System 



Discussions of the thymus gland in its relation to the vegetative nerv- 

 ous system are very fragmentary. The thymus is usually classed as a gland 

 of internal secretion, yet its endocrin nature is doubted by a considerable 

 number of physiologists. Probably the strongest evidence of its produc- 

 tion of an internal secretion has been furnished by Uhlenhuth (c) (d) (e) 

 (/) . His experiments indicate that it produces a substance which causes 

 tetany, and which is counteracted by the parathyroids. But, on teleological 

 grounds, the existence of such a function is doubtful. 



Certain symptoms have been described in hyperplastic conditions of 

 the thymus, such as "thymic asthma," hoarse-ness, stridor, dyspnea, and 

 eosinophilia, which cannot all be accounted for on the ground of pressure, 

 and which have caused Wiesel (&) to suggest that the thymus probably sup- 

 plies the blood with a parasympathicotropic substance. The thymus is 

 classed by many investigators as a parasympathicotropic gland. 



