230 Cc. M. JACKSON 
ume. Hypertrophy of the suprarenal gland (especially of the 
cortex) during pregnancy has been described by various authors. 
Elliott and Tuckett (06) found great variation in the relative 
volumes of cortex and medulla in the suprarenal gland of adult 
animals. Thus the medulla varies from 1.6 per cent of the gland 
in the guinea-pig to 50 per cent in the fowl. In the adult rat the 
medulla forms about 5 per cent of the gland. In very young 
mammals the medulla is relatively larger, the growth of the su- 
prarenal after early youth being apparently in the cortex alone. 
They also noted a relatively larger suprarenal in the female, 
ascribing this to pregnancy.* 
Bager (’17) found the suprarenal glands of the rabbit relatively 
heavier in the female after the age of puberty. 
A relative increase in the amount of cortex, with corresponding 
decrease in the relative size of the medulla in the suprarenal gland 
according to age, was previously noted by Canalis (’87) in the 
rabbit, and by Hultgren and Anderson (’99) in various mam- 
mals, especially cat and rabbit. Soulié (’03), however, describes 
the suprarenal medulla as relatively small in the human fetus, 
forming hardly 10 per cent in the new-born, the proportion be- 
ing a little higher in the adult and relatively greater in other 
mammals. Scheel (’08), Starkel and Wegrzynowski (10), 
Thomas (’11), and others describe a relative increase in the post- 
natal human medulla (which will be considered later under 
‘Morphogenesis of the suprarenal gland’). Gottschau (’83), by 
comparison of the relative widths of cortex and medulla in sec- 
tions of the suprarenal, concluded that there is great variability 
in different mammals. Pfaundler (’92) found the ratio of cortex 
to medulla in the suprarenal of the horse to be variable, the aver- 
age being about 4:1, which is nearly in agreement with the data 
of Flint (’00) for the dog. In the rabbit, Bager (’17) found the 
medulla to decrease in relative size from 20.8 per cent of the 
gland in the new-born to 1.84 per cent at one year. No differ- 
ence was noted according to sex in the ratio of cortex and medulla. 
On the whole, therefore, the evidence would appear to support 
the conclusion that in general the suprarenal medulla in mammals 
3 See footnote on page 229, 
