HORMONES, DRUGS, AND TOXINS 721 



The experiments of Cohnheim, confirmed by Hall (see references in Levene 

 and Meyer's paper, 1911), showed that, while the addition of muscle plasma or of 

 pancreatic extract to solutions of glucose had practically no effect in causing 

 fall in copper-reducing power, mixtures of the two had a considerable effect. The 

 conclusion was naturally drawn that the effect of the pancreas was to facilitate 

 the consumption of glucose by the muscles. But Levene and Meyer (1911) 

 found that the reducing power of such sugar solutions after action of combined 

 muscle and pancreas extracts was restored to its original height by boiling with 

 1 per cent, hydrochloric acid. Further, the apparent disappearance was only to be 

 obtained with concentrated glucose solutions. If the product of the action of the 

 combined extracts was diluted ten times and allowed to stand, the original 

 reducing power returned. It was evident, therefore, that the effect was due 

 to the activation of some enzyme system, which acts, as usual, in a synthetic 

 manner on glucose, in a hydrolytic manner on the disaccharide formed in 

 concentrated solutions of glucose. Further experiments showed that dilute 

 solutions of maltose were hydrolysed by the mixture, whereas it was shown 

 later (1912) that lactose was not so hydrolysed, and that synthesis occurred neither 

 with mannose, xylose, ribose, nor galactose, but that it did with fructose. The 

 experiments, interesting in themselves, show that the phenomenon has nothing 

 to do with diabetes. 



The next point that comes up for discussion is the origin of the hormone, 

 since there are two different tissues in the pancreas, the cells which secrete the 

 digestive juice and the structures called the " islets of Langer harts." Although 

 it had been suggested that these latter are the organs which secrete the anti- 

 diabetic hormone, certain observers had advocated the view that they do not 

 constitute a tissue sui generis, but are produced from the ordinary alveoli of the 

 gland. The question was finally decided by the work of Homans (1912). The 

 results of Bensley, showing that the islets could be stained selectively, both 

 after fixation and by intravital injection of methylene blue, neutral red, or 

 pyronin, were first confirmed, so that it was possible to detect changes in the 

 size or number of the islets. If the gland is excited to prolonged activity with 

 secretin, no change in the islets can be detected. If only a small part of the 

 gland is left in an animal, no conversion of acinous tissue to islet tissue occurs, 

 as might be expected to happen if it were possible. Previous investigators had 

 found that the pancreas, by injection of paraffin into the ducts and so on, could 

 be reduced to a state in which no normal acinous tissue could be found, although 

 the islets remained and no diabetes occurred. Homans points out, however, that 

 the decisive proof of the connection of the islets with carbohydrate metabolism is 

 not hereby given unless it is shown that the remains of the gland acini play no 

 part and could be removed without diabetes occurring. At the same time, 

 evidence distinctly points to the islets as the responsible tissue. Fig. 257 

 reproduces three of those given by Homans. 



Interrelation of Internal Secretions. Various statements have been made as to 

 the mutual relation of these organs, especially by Eppinger, Falta, and Rudinger, 

 who have based elaborate theories on very slender evidence. Elliott (1913, p. 320) 

 justly warns against building on insecure foundations, saying, " Medicine owes no 

 debt of gratitude to those who teach to her theories without proof." 



Nevertheless, as Elliott himself (1913) points out, there are common features 

 which suggest a common bond : 



(1) Carbohydrate metabolism is influenced, not only by the pancreas, but also 

 by the thyroid in superactivity, in acromegaly, and by the injection of adrenaline. 



(2) Growth is affected by the testis and the cortex of the suprarenals, arrested 

 by absence of the thyroid. 



(3) Nervous implications. 



(4) The pituitary becomes hypertrophied when the thyroid is removed. 

 Acromegaly may lead to enlargement of the thyroid. 



(5) Gaskell (1908, p. 430), on morphological grounds, classifies together the 

 suprarenal cortex, the pituitary, and the thyroid as being modified from the coxal 

 glands, the primitive excretory organs of the ancestral arthropod. 



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