Findlay, in his admirable historical survey of rickets,1 defines this disease as a derangement of which the chief manifestation is to be seen in the growing bone, in which there is an excessive and irregular development in its earlier stages, with arrest or delay in the formation of fully-formed, firm and normally calcified bone.

As long ago as 1650 the symptoms were described with accuracy by Glisson,2 of whose description Findlay makes the comment that "there has been nothing to withdraw and very little to add." With regard to the external appearance of a rachitic child Glisson states:

The parts of the child are irregular and of unusual proportion. The head is larger than normal, and the face fatter in respect to the other parts. The external members and muscles of the body are seen to be delicate and emaciated The whole skin, both the true and the fleshy and fatty layers, is flaccid and rather pendulous, like a loose glove, so that you think it could hold much more flesh. The joints are not firm or rigid. The chest externally is thin and much narrowed.

The disease is further characterized by restlessness and perspiration at night, and occasionally by sensitiveness of the limbs so that the child cries on being handled. Many writers describe gastrointestinal disturbances as characteristic of rickets, but Findlay states that in his experience normal digestion is the rule rather than the exception, the characteristic protruding abdomen being due partly to degenerative changes in the walls of the stomach and intestines and partly to the abnormally small size of the thoracic cavity. It may be noted in this connection that scurvy and rickets are not infrequently found in conjunction and the symptoms of the one may very easily have been occasionally confused with symptoms of the other.

The ends of the long bones are enlarged, especially at the wrists and ankles, and the bones themselves are variously distorted. A curious feature of the disease is the fact that the various bones seem to be unequally affected in different cases. In one case the legs may suffer chiefly, in another the arms, in still another the thorax, and in others again the head; nevertheless, in not a few cases, all parts of the skeleton are equally and severely affected.3 Very characteristic is the "beading " of the ribs, due to the development of nodules at the juncture of the ribs with the costal cartilages, which if very prominent may be seen as a string of beads down each side forming the "rickety rosary".

1 Med. Res. Com. Sp. Rep. 20.

2 Glisson, De rachitide, London, 1050.

Analysis shows that the rachitic bone is strikingly deficient in calcium. Langstein and Meyer4 give the following results for the analysis of a rachitic and a normal bone:

Owing to this deficiency the rachitic bones are soft so that they can readily be cut with a knife and bend easily. The following clear description of the bony structure is taken from Pindlay (1. c.):

Macroscopic Characters

On section of any long bone the most striking abnormality is the increase in width of the cartilaginous growing sone. Normally, this growing sone is truly a line - the epiphyseal line - forming a narrow, glistening, bluish-white band, sharply demarcating the diaphysis from the epiphysis. In rickets it is increased in thickness many fold, is irregular, and extends by tongue-like processes into the diaphysis. Sometimes these areas of cartilage are completely cut off from the growing epiphyseal sone and, as suggested by Virchow, may form nuclei for the development later of enchon-dromata. Occasionally this hyperplastic tissue retains the appearance of having been deposited in layers, the one layer being separated from the other by a vascular sone. More frequently, however, no such arrangement is visible, and irregular islands of uncalcified cartilage separated by vascular spaces predominate. These vascular areas give the idea of hyperaemia, and have suggested the view that the condition is inflammatory in nature.

The narrow cavity seems unduly wide, and there is the appearance of increased bony tissue under the periosteum.

Microscopic Characters

On microscopic examination the irregularity of the epiphyseal sone is even more striking.

At the growing end of the shaft of any long bone of the normal child the first change observed is a proliferation of the cartilage cells, which subsequently become arranged in rows in the long axis of the bone. The cell spaces enlarge and become confluent, forming the primary narrow spaces. The cartilage cells then degenerate, and the spaces are invaded by vessels from the perichondrium, accompanied by osteoblasts and connective tissue. The vessels of the perichondrium encircle the bone in rows as hoops do a barrel, and thus the invading vessels are arranged at different levels and give to the bone a somewhat striated appearance* These branches enter the bone at right angles to the long axis, and ramify in the primary marrow spaces; they do not anastomose, but terminate as end arteries. According to Schmidt, these vessels vary in number in different bones, and their relative abundance is a measure of the rate of growth of the bone. The cartilaginous matrix between the cells next becomes calcified, and these pillars of calcified cartilage form a scaffold on which bone is deposited.

The normal body trabeculae thus formed are occupied for the most part by almost parallel rows of elongated bone cells, with their processes running at right angles to the margin, and are surrounded by a mere rind of homogeneous "osteoid" tissue.

3 Findlay, 1. c.

4 Langstein and Meyer, Saugtingsernahrung and Sauglinsstoffwechsel. Wiesbaden.

In rickets there is an excessive preparation for the formation of bone in the greatly increased depth of the layer of proliferating parallel-arranged cartilage cells. The disappearance of the cells is delayed, and occurs erratically, so that irregular areas of cartilage remain as such, and are neither absorbed nor infiltrated with lime. These tongue-like processes of cartilage alternate with areas of partially or almost normally calcified tissue, with an apparent increase of the intervening marrow. When ossification occurs it takes place irregularly. The trabeculae persist for the most part, however, as homogeneous processes with or without ghosts of cartilage cells - the so-called osteoid tissue - with small central sones occupied by dwarfed and irregularly placed bone cells.