74Q A MANUAL OF VETERINARY PHYSIOLOGY 



first week, and up to the end of the first year will add 0*2 kilo- 

 gramme (0-44 pound) daily to its body weight. 



The relative rate of growth of each part is not the same. 

 The eyes, ears, brain, kidneys, and liver grow less rapidly than 

 the other parts, owing to their relatively large size at birth. 

 The greatest increase is in the skeleton and muscles, and to the 

 rate of this increase we have just alluded ; the least increase is 

 in the eyes and the ears and the limbs below the knee and hock. 

 Few observations have been made on the rate of growth. 

 Percival* many years ago drew up a table, which he considered 

 very imperfect, as to the rate at which some horses of his regi- 

 ment grew, from which he showed that the increase in height 

 between two years and three years was on an average 1 inch, 

 between three years and four years J inch, and between four 

 years and five years J inch. Some of the horses did not grow. 



Of 35 two-year-olds, 2 did not grow during the year. 

 Of 144 three-year-olds, 17 did not grow during the year. 

 Of 48 four-year-olds, 7 did not grow during the year. 

 Of 1 1 five-year-olds, 2 did not grow during the year. 



There can be no doubt that many horses grow much more 

 than § inch between three and five years, and many grow up to 

 their sixth year. 



The writer measured the daily growth of a foal for three months, 

 the observations being made at the withers and croup. The 

 animal during this period grew, on an average, one inch every 

 eight days. The most rapid growth occurred shortly after birth 

 and was one inch in three days. Both at the withers and croup 

 the rate of growth was practically equal. 



During the time the calf and foal are receiving their mother's 

 milk the urine is acid, for the reason that the animal is prac- 

 tically carnivorous. Once a vegetable diet is taken, the urine 

 becomes alkaline and, it is probable, decreases in quantity. The 

 activity of certain glands, such as the thymus, becomes con- 

 siderably reduced as the animal grows, and finally disappears 

 at the adult period. One characteristic of the young animal is 

 the necessity for sleep. It is probably during slumber that the 

 tissues make the immense strides noticeable during the first few 

 weeks of life. 



Dentition commences immediately at birth, if it has not already 

 commenced in utero. The following tables show the period at 

 which changes take place in the teeth from birth to adult age. 



The periods of eruption and change of the molar teeth are 

 liable to considerable variation. 



* ' Lectures on Form and Action.' 



