HORMONES, DRUGS, AND TOXINS 733 



against the necessity of assuming specific " opsonins " is given by Savchenko and 

 Aristovsky (1912). They show that the optimum reaction of the medium for 

 phagocytosis is the same as that most favourable for the adsorption of the " alexin " 

 by the object of phagocytosis ; and that phagocytosis, as showing itself by the 

 mutual attraction (relative surface tension) of the leucocytes and the object, and 

 by the moistening of the object by the protoplasm of the leucocyte, depends on the 

 adsorption of the alexin by the object of the phagocytosis. The meaning of the 

 " alexin " requires further investigation. 



SUMMARY 



There are a large number of substances, acting powerfully in minute amount, 

 which are of great importance in physiological processes. 



One class of these consists of the hormones, or chemical messengers, which are 

 produced in a particular organ, pass into the blood current, and produce effects 

 in distant organs. They provide, therefore, for a chemical co-ordination of the 

 activities of the organism, working side by side with that through the nervous 

 system. 



The most typical instance of this kind is the pancreatic secretin. Methods of 

 preparing active secretin solutions, free from the depressor substance, are given in 

 the text. 



There is evidence that a similar substance is produced from the pyloric mucous 

 membrane, and excites the secretion of gastric juice. 



The internal secretions, formed by ductless glands, as well as by other tissues, 

 belong to the class of hormones. 



The remarkable relationship of the medulla of the suprarenal glands and its 

 secretion, adrenaline, to the sympathetic system is discussed in the text. 



Certain drugs, such as nicotine and pilocarpine, produce a part of their effects 

 - by stimulating the secretion of adrenaline into the blood. 



The respiratory centre is stimulated by the increase of hydrogen ion concentra- 

 tion in the blood, due mainly to carbon dioxide, a parahormone, in Gley's sense. 

 There is no satisfactory evidence of its acting as a specific hormone. 



The various hormones arising from the sexual glands are responsible for the 

 development of the secondary sexual characters, 'ihese hormones appear to be 

 produced by the interstitial cells, not by the generative cells themselves. The 

 corpora lutea of the ovary are responsible for the first stages of uterine hypertrophy 

 and for the growth of the mammary gland. 



There are certain " ductless glands," pituitary, thyroid, and thymus, which 

 have a marked influence on growth in general. 



Complete removal of the pancreas results in the production of severe diabetes. 

 The structures responsible for the " antidiabetic " hormone are the islets of 

 Langerhans. 



There are interrelations between certain of these internal secretions, but, 

 at present, their nature is still very obscure. 



Some evidence exists of the production of hormones in plants. 



The mode of action of drugs is discussed in the text. The conclusion arrived 

 at is that the chemical structure alone throws very little light on their action. 

 The theory of " chemo-receptors " or special receptive side-chains in the cell 

 is found to be contrary to many facts, and to be generally inappropriate. While 

 the cells take up certain alkaloids, such as atropine, which can be regained from 

 them, they do not take up any detectable amounts of strophanthin, which acts in 

 direct proportion to its concentration outside. It is probably adsorbed at the 

 cell membrane. 



In the explanation of " specific " action, phenomena due to surface action, and 



