20 



FARMER'S CYCLOPEDIA OF LIVE STOCK 



same function. It is a grayish red or- 

 gan which is highly developed in the 

 fetus and young animal but gradually 

 disappears before adult age. The 

 thyroid also lies on the windpipe and 

 secretes a fluid which is absorbed by the 

 blood and seems to be necessary to 

 the proper assimilation of food and to 

 the physical and mental development of 

 the animal. 



The respiratory organs include the 

 nose, larynx, trachea or windpipe and 

 lungs. The trachea forks into bronchi 

 and bronchioles of smaller and smaller 

 size ending in the alveoli or blind sacs 

 of the lungs. In fowls there are numer- 

 ous extensions of the respiratory sys- 



The kidneys of sheep, goats and swine 

 are bean shaped and without lobes. 



The reproductive apparatus consists 

 of ovaries, oviducts, uterus or womb and 

 vagina in the female; and testes, sper- 

 matic cords, seminal vesicle and penis 

 together with various connecting glands, 

 especially prostate gland and Cowper's 

 gland, in the male. In fowls there is no 

 urinary bladder but the ureters open 

 into the cloaca or posterior part of the 

 rectum. The vagina and uterus are also 

 wanting in fowls, the oviducts opening 

 directly into the rectum. The male 

 copulating organ is absent except in 

 ducks, geese, swan and the ostrich. 



The skin or general integument pos- 



Fig. 13 MERIXO SHEEP 60 YEARS AGO 



tern, known as air sacs, and located in 

 the body cavity and also in the hollow 

 bones. The air sacs communicate with 

 the lungs but not with one another. 



The urinary organs f farm animals 

 consist of kidneys connecting by means 

 of ureters with a bladder from which 

 the urethra conducts the urine to the 

 outside. In the male the urethra passes 

 through the penis and in the female it 

 ends just above the opening of the va- 

 gina. The kidneys are usually enclosed 

 in a capsule of fat. The right kidney 

 of the horse is heart shaped, the left 

 bean shaped. Each kidney of the ox 

 shows 15 to 20 lobes and is oval in form. 



sesses two layers, the cutis and the sub- 

 cutis, the first of which is further sub- 

 divided into epidermis and corium. 

 The subcutis may carry much fat tissue 

 and gradually passes into the dermal 

 muscles and other tissue. The skin 

 musculature is extensively developed in 

 farm animals. Hair, wool, feathers, 

 claws, hoofs and horns are the most im- 

 portant epidermal structures developed 

 in the skin. The bony core of the horn 

 is an outgrowth of the frontal bone. 



Process of nutrition — The farmer is 

 not interested in all the problems of ani- 

 mal physiology. He is chiefly concerned 

 with the processes of nutrition, growth 



