5S8 THE PHYSIOLOGY OF REPRODUCTION 



parturition the pressure falls, but rises again on the third day of the 

 puerperium. 



The effects of pregnancy in the human female on the heart have 

 been the subject of a recent monograph/ to which the reader is , 

 referred for details.. So far as the normal heart is concerned the 

 effects may be summarised as follows : There is no change in the 

 circulation during the first months of pregnancy. After the sixth 

 month the response to effort is restricted: breathlessness appears 

 after an effort which can be accomplished in comfort by a normal 

 non-pregnant woman. There is no hypertrophy of the left ventricle. 

 Owing to the displacement of the abdominal viscera the shape of 

 the chest is altered, so that there is. a displacement of the heart. 

 The apex beat may be pushed out one inch beyond the left nipple 

 line, and this has led to the erroneous supposition of the occurrence 

 of a hypertrophy. Similarly an increased area of dullness to the 

 right of the sternum can usually be made out.^ This also is due to 

 the abnormal position of the heart, and is not to be interpreted as 

 a dilatation of the right ventricle. There is venous stasis, probably 

 due to pressure on the pelvic veins, and a tendency to dropsy, the 

 cause of which is not clear. 



Varices of the lower extremities and external genitals are frequent 

 in human pregnancy. They are due mainly to the increased intra- 

 abdominal pressure and the stretching of the abdominal wall. 

 Secondary thromboses are common in the puerperium. 



(c.) The Ductless Glands. — There is regularly a swelling of the 

 thyroid gland in pregnancy (Tait ^), which consists of a simple hyper- 

 trophy, and not a vascular engorgement or cystic change (Freund *). 

 It has been shown experimentally in cats that a remnant of the gland, 

 which is sufficient to maintain health in the non-pregnant state, is 

 insufficient after the onset of pregnancy (Lange^). Herring's" 

 observations on pregnant rats show no increase in size and no 

 histological changes indicating an increase of secretion. The adrenals, 

 however, showed a slight increase in weight and the load of adrenalin 

 was slightly higher. The hypercholesterinsBmia of pregnancy seems 

 to suggest that there are probably functional changes in the 

 adrenal cortex. The pituitary body of pregnant rats is diminished in 

 size by about twenty-four per cent. This diminution affects mainly 

 the glandular lobe, which shows a great diminution of the granular 

 eosinophil cells. The human pituitary is stated to be enlarged in 



' Mackenzie (Sir J.), Heart Disease and Pregnancy, London, 1921. 



^ V. Winckel, Handimch der Geburtshillfe, vol. i. 



^ Tait, "Enlargement of the Thyroid Body in Pi'egnancy," Obstet. Jow., 1875. 



* Freund, "Ueber die Beziehung der Schilddriise, etc.," Deuts. Zeitsoh. f. 

 Chir., vol. xxxi., 1890. 



" Lange, "Die Beziehungen der Schilddriise zur Schwangerschaft," Zeitsch. 

 f. Gehurtsh. u: Gynak., vol. xl., 1899. 



" Herring, loc. cit. 



