578 INTERNAL SECRETION 



later develop into severe spasms which affect the whole body 

 and resemble epileptiform convulsions. During the progress of 

 these symptoms there is a marked loss of appetite and wasting. 

 In exceptional cases the acute stage is less marked or even absent, 

 and the animal passes into a chronic condition of cachexia ; its 

 fur becomes dry and unkempt ; its nutrition is impaired ; its 

 intelligence is dimmed, and its movements lack precision. The 

 nervous control of the temperature of the body is imperfect ; 

 this is shown by the subnormal temperature. The disease in many 

 features resembles myxcedema, and generally ends fatally within 

 one or two months. 



In herbivorous animals the loss of the gland is followed by 

 a slow development of the cachexia. No disturbance whatever 

 may be observed in some cases ; this has been explained by the 

 discovery of accessory thyroid glands, which are frequently present 

 in rabbits. 



In consequence of the many evil effects which arose from re- 

 moval or disease of the gland, attempts were made to ingraft the 

 gland. The operation produced good but not permanent results, 

 for the gland in most cases failed to grow and was absorbed. 

 Extracts of the thyroid gland were, therefore, given subcutaneously 

 by Murray of Newcastle-on-Tyne, and this method of treatment 

 was highly successful in cases of myxcedema. Patients were then 

 fed on fresh thyroid glands from sheep, and even better results 

 followed. How great is the improvement produced in cases of 

 myxcedema and cretinism is shown by the numerous records and 

 photographs of patients before and after treatment with extracts 

 of the thyroid gland. It is clear from these cases that the 

 effects are far-reaching, and influence both the bodily and 

 mental development. The fact that the administration of the 

 gland must be continued throughout life indicates that the 

 nutrition of the body demands a constant supply of some 

 substance yielded by the thyroid gland. 



What, then, is the specific substance produced by the thyroid 

 gland ? An answer to this question must be sought in the 

 structure and chemical composition of the gland. The thyroid 

 body is a ductless gland, and the so-called " colloid," which fills 

 the acini, is its " internal secretion." The colloid is apparently 

 derived from the granules which can be seen in the cells of the 

 acini, and is discharged into the acini, where it accumulates until 



