ADDENDA 



HERE I have summarized a few papers which I came 

 across too late to insert in the body of the book. 

 Owing to an oversight, the valuable work of Robb 

 (1929) has not been adequately discussed in the text. It has 

 very interesting bearings on the relation of heterogon to endo- 

 crine control (see Chap. VI, §4). He investigated the growth 

 of various organs in a large (Flemish) and small (Polish) 

 breed of rabbits, reaching about 6 and 3 kg. adult weight 

 respectively, and in their F x hybrids. 



He first found that the pituitary (weight) shows simple 

 negative heterogony relative to (clean) body- weight, with the 

 same growth-coefficient (k = 0-55) in all three types ; the 

 curves all have the same point of origin. Adrenal weight 

 shows simple positive heterogony, but k is higher for the small 

 breed (1-34 as against 1-19 for the Flemish). As a result the 

 relative weight attained by the adrenal in the adult Polish 

 is just double what it is in the adult Flemish (0-2 as against 

 o-i per cent) ; the hybrids show an intermediate value. The 

 difference is due almost exclusively to an enlargement of the 

 cortex. 



The growth of the thyroid falls into two phases, one of 

 negative heterogony (k about 0-53) up to about 600 g. body- 

 weight, and one of positive heterogony (k about 1-12) from 

 then on. 



The testis, like the adrenal, attains a higher relative weight 

 in the dwarf than in the giant race (0-3 as against 0-12 per 

 cent, with a value of 0-2 in the hybrids), and the heterogony 

 curves against body- weight are, of course, very dissimilar in 

 the two breeds. But when testis weight is plotted logarith- 

 mically against adrenal weight, the two breeds show almost 

 identical curves, negatively heterogonic (k = 0-74) up to 40 

 days of age, then with very high positive heterogony (k = 2-3). 

 Testis weight against pituitary weight, on the other hand, 

 shows k = 1-4 up to 40 days, but then k = 5-1 for the giant, 

 5-8 for the dwarf race. This appears to indicate a more 

 marked interdependence of testis and adrenal cortex than of 

 *7 2 57 



