150 The Irish Naturalist. [June, 



THE CROOKEDNESS IN THE STERNA OF CERTAIN 

 BREEDS OF DOMESTIC FOWLS. 



BY PROF. R. J. ANDERSON, M.D. 



Ordinary Barn-door Fowls have usually sterna with straight 

 keels, and the tail bones are set commonly in the same vertical 

 plane as that in which the vertebral column is situated. 

 Crooked keels are very common amongst the pure breeds. 

 What is the cause of the asymmetry? The nature of the 

 roosts, the early roosting of the birds, the nature of the breed, 

 the weight of the birds, the proximity of the roosts to the 

 w^alls of the fowl house, the state of health of the birds due to 

 the season or the time of hatching, or to the presence or 

 absence of certain substances such as lime in the food, or 

 w^ant of iron, or a rickety condition of the skeleton, due to 

 close interbreeding, may have an effect. Animals in our own 

 climate are much subjected to unnatural conditions (too little 

 fresh air and too much moisture are often causes of unhealth) ; 

 it is necessar>^ to take account of such factors in at- 

 tempting to ascertain the cause of the anomalies such as 

 the skeleton presents. It is also necessary to take note of 

 the fact that the isolation of certain breeds means more than 

 the separation of birds having certain colours or great local 

 growths of feathers or grotesque wattles. The cultivation of 

 a colourless or white breed of fowl may mean the perpetuation 

 of an imperfectly' pigmented nervous system, and although 

 pigment and lime do not appear to be necessary to each other, 

 it would seem that phosphates and phosphoretted fats 

 promote the efficiency of the nervous system. The 

 increased growth of wattles or feathers is also associated with 

 activities of another kind, which, if the skeleton do not 

 experience a corresponding increase in vigour, may actually 

 lead to a weakening of the bones. C. Darwin showed long 

 ago how the skeleton varied in rabbits, &c., under domestica- 



