328 



CELLS, TISSUES, AND ORGANISMS 



of low-level feeding, with the resumption of high-level feeding much 

 of the weight may be made up again. But if the underfeeding takes 

 place in a critical period of the animal's life, the composition of the 

 live weight will be altered, as we shall see. 



Body proportions 



As an animal grows up, its body proportions and composition 

 change. These alterations are brought about by a differential rate of 

 growth occurring in the different parts and tissues of the body ( Figure 

 7). The order in which -the various parts and tissues develop is much 

 the same in all species, for it is based on the relative importance of the 

 functions of the parts or tissues for survival of the animal. 



The changes in the form of the embryo as it develops repeat, in 



UJ 



or 



lij 



Q- 



I- 

 X 

 C£ 



UJ 



< 

 CD 



1 



AGE FROM CONCEPTION TO MATURITY 



A = EARLY MATURITY-HIGH PLANE OF NUTRITION 

 B = LATE MATURITY-LOW PLANE OF NUTRITION 



12 3 4 



HEAD 



NECK 



THORAX 



LOIN 



BRAIN 



BONE 



MUSCLE 



FAT 



CANNON — TIBIA-FIBULA— FEMUR 



PELVIS 



KIDNEY-INTERMUSCULAR-SUBCUT 

 FAT FAT FAT 



MARBLING 

 FAT 



Figure 7. The growth curves of different tissues and parts of the body of 

 the sheep under high and low levels of nutrition. (Palsson, 1955.) 



