SOURCES OF INFORMATION 1(J 



functional and anatomical destruction was tried upon the internal 

 secretory organs. But the results of a large number of experi- 

 ments did not contribute very materially to the solution of the 

 problems under discussion. In the most favourable instances, 

 the destruction of tissue elements by specific cytotoxic sera merely 

 confirmed the results which had been obtained in other ways. 

 A closer study of their action showed that, though they have 

 an affinity for the organic cells, this affinity is by no means 

 confined to specific organs. Moreover, the cytotoxic sera nearly 

 always contain ha^molysins and other components, which exert 

 a toxic influence upon other organs. 



A more satisfactory method is the elective destruction of 

 certain tissue formations by means of the Rontgen rays. Very 

 interesting results have already been obtained and it is probable 

 that this method will contribute largely to our knowledge of the 

 internal secretory activity of certain tissue elements. 



Extirpation is attended by certain by-effects by which the 

 results of experiment may be prejudiced. These are : The degree 

 of surgical shock; derangement of the circulation; and injury to 

 the nerves. In human pathology, when any organic function is 

 suddenly suppressed, an important factor is supplied by the 

 vicarious intervention of another organ possessing the same or 

 a similar function ; but it must be borne in mind that such inter- 

 vention is hardly to be expected in the case of the lower animals. 



For this reason, partial destruction especially the destruction 

 of one of a pair of organs will be found to yield very suggestive 

 results. The compensatory hypertrophy of the other one of the 

 pair is a proof of their functional relationship. 



Compensatory or correlative hypertrophy (which is the 

 anatomical expression of the functional over-activity of a tissue) 

 appears primarily in the accessory organs, in tissues of a similar 

 structure belonging to the same system, or, in the case of the paired 

 organs, in the sound half of the pair. But where there is under- 

 activity of any organ possessing chemical functions, tissues of 

 entirely different structure may vicariously intervene and may even, 

 as a result, become hypertrophied. An instance of this is the 

 hypertrophy of the pituitary gland which follows extirpation of the 

 thyroid. Finally, processes of growth may lead to hypertrophy 

 in individual organs, if the function of another chemically cor- 

 related organ becomes deranged, thus increasing or diminishing 

 the amount of hormone which it supplies. In such a case there 

 is no compensatory activity on the part of the hypertrophied 

 organ. The cardiac hypertrophy which accompanies hypertrophy 

 of the thymus, as in the status thymicolymphaticus and the 

 well-known "goitre heart," is an instance of such a condition. 

 The cardiac enlargement in these cases may be due to the con- 

 tinued over-production of substances which stimulate cardiac 

 activity. 



