132 



PHYSIOLOGY FOR DENTAL STUDENTS. 



active principle of these extracts has not as yet been isolated, 

 although the extracts can be considerably concentrated, thus 

 yielding the trade preparation called pituiirin. 



It is particularly interesting to note that although the anterior 

 lobe does not yield any active extract, yet its excision is fatal. 

 On the other hand, the posterior lobe can be removed with im- 

 punity, although extracts of it have profound physiological 

 effects when they are injected into normal animals. 



A. 



B. 



Fig. 12. A, To show the appearance before the onset of acromegalis symp- 

 toms: B, The appearance after seventeen years of the disease. (Aftei 

 Campbell Geddes. ) 



The Spleen. Notwithstanding the fact that this is the larg- 

 est of the ductless glands, it is the one whose functions are the 

 least well understood. It can be excised without causing any 

 evident disturbance, and extracts of it when injected intraven- 

 ously do not have any characteristic effects. It becomes very 

 much enlarged in certain diseases, namely : ( 1 ) in leucocythe- 

 mia, a form of anaemia, which is characterized by a great increase 

 in the leucocytes of the blood (see p. 145) ; (2) in typhoid fever 

 (enteric fever) ; (3) in malaria. It becomes contracted after 



