Findlay (2) points out that rickets is almost entirely limited to the northern hemisphere, and that it is in great measure restricted to the temperate zone. At present it is a veritable scourge among the children of many parts of Europe owing to conditions brought about by the war. It is common in most parts of Europe except in southern Spain, southern Italy, and Portugal. It appears to be rare in the West Indies, most parts of South America, the Philippines, a large part of China, India and the Malay peninsula. Sporadic cases occur in all these places. Mellanby (9) states that in the west of Ireland the disease is unknown. Rickets is said to be much rarer among Jewish children than among other elements in the population.

Rickets.

Normal Legend descriptive of illustrations of normal and rachitic bones, shown on pp. 297-298.

To show the differences between a rachitic and a normal bone. In the shaft (dia) and the center of ossification (co) of the epiphysis (ep), calcified tissue is black and osteoid tissue red. The zone of provisional calcification is absent from the rachitic bone, and the proliferative zone of cartilage (pz) is prolonged as an irregular mass of cartilage which is ragged and inter-digitates with tongues of osteoid tissue. A metaphysis is formed. The cortex (cor) is thickened though the bone in it is very thin. The trabecule are surrounded by osteoid.

c....Resting cartilage.

co...Center of ossification.

ep...Epiphysis (head).

met.. Metaphysis.

dia...Shaft (diaphysis).

zc...Provisional zone of calcification.

pz...Proliferative zone of cartilage.

T...Trabecula.

cor...Cortex of shaft.