940 Rachitis. 



velops instead a spongy, soft, red tissue, certainly more than 

 a centimeter wide, ■vi^hich passes into cartilage and bony tissue 

 without any sharp border or in irregular streaks. The con- 

 nection between Epiphysis and diaphysis appears loosened, so 

 that they can often be separated with slight exertion ; this may 

 even take place during the life of the animal and then the 

 epiphysis will lie laterally to the diaphysis. The yellow marrow 

 of the long bones is more or less reddened and gelatinous if 

 the animal is notably emaciated. The spongy bone substance 

 is also reddish in color and shows a raritication of the cancellous 

 portion. The joints present, not infrequently, signs of inflam- 

 mation and of ulcerative destruction of the cartilages. 



The flat bones, especially the upper bones of the skull and 

 the pelvic bones, are thickened, sometimes enormously bulged 

 out, and changed to a lardaceous, grayish-red to dark red, firm 

 tissue, which can be cut and which is covered only in spots by 

 a flexible and porous cortical substance, while in other^p^aces 

 it passes into the adjacent soft parts and contains only 

 isolated bony islands. Owing to the bulging of the bones the 

 nares and the maxillary sinuses are small or even obliterated, 

 and in pigs the palate furthermore bulges into the oral cavity. 

 Sometimes the proliferating tissue of the maxillary bones con- 

 tains cysts which have developed from hemorrhagic foci 

 (Hintze, Willies). The teeth are placed rather deep and lie 

 loose in the proliferating tissue, without any alveolar borders ; 

 their enamel surface in the pig is uneven, pitted, honeycombed, 

 or in exceptional cases the enamel layer may be entirely absent 

 (Preuss). Sometimes the skull bones are soft and moderately 

 thickened, in exceptional cases they may have become so rarified 

 that in spots only a thin, connective tissue-like membrane (the 

 single or the double periosteum) remains visible (Craniotabes), 

 and in such cases there are usually also signs of hydrocephalus 

 internus (Schiitz). The other flat bones, especially those of 

 the pelvis, may also be bent in various directions and present 

 similar changes in their substance as those in the skull bones. 



The microscopic changes in the long bones (Kg. 159) may be summed 

 up as follows: Starting from the periosteum there develops a cellular and 

 vascular osteoid tissue containing comparatively large osteoblasts and bone cells 

 in varying numbers. In the diaphyseal part of the cartilage the cartilage cells 

 are larger, arranged in waVy streaks, and similar cartilage-islands extend toward 

 the marrow. From the marrow numerous vessels, with thin walls and surrounded by 

 cellular tissue, enter deeply into the cartilage tissue, opening the cartilage cell col- 

 umns, often in an oblique direction. Similar vessels may proliferate into the interior 

 of the cartilage tissue, even from the perichondrium and loosen this in their vicinity 

 which becomes softened. The layer of calcification between bony and cartilaginous 

 tissue is either entirely absent or there are only isolated foci of calcification; 

 instead there is a very wide layer of osteoid tissue which is similar in structure to 

 the layer starting from the periosteum, and is later partly changed into more solid, 

 bony tissue. 



In the so-called snuffles or maxillary rachitis of pigs a transitional zone with 

 smaller decalcified bony laminae is joined to the zone of normal bony tissue, 

 upon which follows a tissue similar to sarcoma, consisting basically of spindle cells 

 or cells of various shapes, rich in protoplasm and containing large nuclei. In 

 this proliferating tissue there are seen numerous osteoid laminae which gradually 



