118 VITAMINS A AND CAROTENES 



retardation and failure of Haversian system formation resulting in arrest- 

 ment of compact bone formation, and continuation of appositional bone 

 formation. The total effect is that of thicker, coarser, and shorter bones, 

 less graceful in appearance than corresponding normal bones because of 

 failure of resorption, wherever that is scheduled as a featiu'e of normal 

 growth, conspicuously at the ends of long bones (Fig. 30). In regions where 

 appositional bone formation is the normal process by which bony contours 

 are formed, we find apparently greater rate of bone production. In the 

 long bones such regions are, for example in the rat, the third trochanter of 

 the femur, the crest of the tibia, and the interosseous crests of tibia and 

 fibula. In vitamin A deficiency, with cessation of longitudinal growth these 

 regions present an appearance of excessive rate of growth. Serial sections 

 of petrous bones of normal and vitamin A-deficient rats and dogs have 

 shown that the activity or ' rate of appositional bone formation varies 

 greatly in different regions and that the apparently excessive local bone 

 growths are correctable with the normal rates and patterns of growth. 

 The petrous bone is an interesting, though difficult, region to study because 

 the bony labyrinth of the internal ear is adult size at birth and because it 

 does not undergo remodeling with increase in size of the base of the skull 

 but does change position, moving outward and backward with reference to 

 the body axis. Increase in size and remodeling of the temporal l)one com- 

 plex are features of its growth which are very e\ndent in the recess for the 

 paraflocculus in which appositional bone growth is much greater on the 

 internal (medial) side than on the external (lateral) side. The reverse ap- 

 plies to bone resorption in the recess. The normal pattern of growth of the 

 petrous bone of the rat is somewhat different from that of the dog; in the 

 latter, in vitamin A deficiency, continuation of appositional bone growth 

 causes compression of the eighth nerve, but not in the rat, although com- 

 parable building up of bone occurs in a closely adjacent situation. Thus 

 the untoward consequences of changes in the skull vary with the species. 

 Deafness in dogs'-^^> "''^ and blindness in calves-*^ are early results of the 

 deficiency. Neither occurs in the rat. 



In an impressive study of the ear in rabbits with long-continued \-itamin 

 A deficiency, Perlman-'^''^ has reported the formation of nodular bone forma- 

 tions in the internal auditory meatus, the cribiform plate, the cochlear 

 aqueduct, and the modiolus within the cochlea which cannot be related to 

 normal growth patterns but which can be related to lesions produced in 

 guinea pigs by acidosis and ligation of blood supply reported by other 



28 E. Mollanhy, ./. I'hijsinl. (Loinlon) 94, IWO (1938). 

 " E. Mell'iiihy, ./. I'luiHiol. {London) 99. 467 (1941). 

 28 L. A. Moore, ./. Snlrition 17, 443 (1939). 

 28=' II. B. Perlin,-in, Arrh. Ololanjinjo} . 50. 20 (1947). 



