THE RATE OF GROWTH IN THE HORSE 



293 



Hermit. From the twenty - 

 fourth week onwards the limbs 

 grow faster than the trunk. 

 In front the increase in growth 

 is mainly beyond the wrist- 

 joint, while in the hind-limb 

 it is chiefly beyond the knee- 

 joint or stifle. In both fore- and hind- 

 limbs the increase is greatest for some time 

 in the middle metacarpals (fig. 565, III) 

 and metatarsals i.e. in the fore and hind 

 cannon bones. In the case of Hermit 1 (the 

 1867 Derby winner), when the humerus is 

 taken as equal to 100, the third metacarpal 

 is equal to 76'1. In a seven-months foetus, 

 however, with the humerus equal to 100, 

 the third metacarpal may be over 90, while 

 at nine months it may be over 110, and 

 at birth 130 i.e. relatively well-nigh twice 

 the length of the third metacarpal in Her- 

 mit. A similar rate of growth characterizes 

 the third metatarsal bone. This increase in 

 the cannon bones during the second half of 

 the period of gestation explains to a large 

 extent the great length of the foal's legs at 

 birth; it also accounts for the fact that the 

 cannon bones the bones considered of so 

 immense importance in all kinds of horses 

 increase but little in length after birth. 

 In the case of a thoroughbred, e.g., the 

 third metacarpal appears only to increase 

 3 cm. (barely Ij inch) after birth, 2 while 

 the main bone of the fore-arm (the radius) 

 often increases 9 cm. (3j inches), or nearly 

 three times as much as the front cannon 

 bone. 



fbo* 



Fetlock joint- 



III Digit 



Fig. 565. Fore-limb (twenty-three 

 weeks), natural size 



1 The skeleton of Hermit is preserved in the Royal Veteri- 

 nary College Museum, Camden Town, London. Eclipse's skele- 

 ton is in the Royal College of Veterinary Surgeons Museum, 

 Red Lion Square, London. 



2 Though the cannon bones may only increase 1 inch in length after birth, they may increase 3 or even 

 4 inches in circumference in a 14-hands horse. 



