At the height of the disease the bones, besides being softer, are speci fically lighter than natural, and contain an undue proportion of fatty matter. Moreover, the cartilage contains a high percentage of water. The bone on analysis has been shown to consist of 33 to 52 per cent. of earthy salts, instead of 63 to 65 as in health, and its animal matter is said to yield no gelatine on boiling.
When the disease becomes arrested, ossification in the soft., newly formed tissue takes place rapidly. The loose spongy structure closes up and becomes thick and hard, and the whole bone is heavy and dense.
The morbid changes in the osseous system form, no doubt, the most characteristic feature of the rickety state : but rickets is not merely a dis ease of the bones. In addition, various pathological changes are discovered in the bodies of children who have died while suffering from this affection. In some the liver, spleen, and lymphatic glands are found diseased, the muscular structure is altered in bad cases, the brain may be affected, and the urine almost invariably exhibits pathological characters.
The alterations in the liver, spleen, and lymphatic glands are by no means present in every case, or even in every marked case of the disease. The affected organs are enlarged, tough, and solid to the touch, and heavy out of proportion to their size. The change is usually most marked in the spleen. Dr. Dickinson considers it to be due to no "new growth or infil trated deposit," but to a hyperplasia of the normal tissue of the organ, and chiefly of the interstitial connective tissue. The fibrous and epithelial ele ments are hypertrophied, and at the same time their earthy salts are de ficient in quantity. In the liver the fibroid sheath within the smaller portal canals is twice its natural size, and in the glandular structure the yellowish acini are bounded by a thin pinkish or grayish line. In the spleen the .in terstitial connective tissue may become so hypertrophied that the trabecuku are as thick as the spaces they enclose. In the meshes the corpuscles are seen by the microscope to be crowded together. The organ is hard and resistant, so that it can be cut with the utmost ease into thin sections. Its
surface is deep red or purple in colour, with smooth white spots from en larged Malpighian corpuscles. Its section is deep red mottled with pale buff colour. But little blood can be squeezed from the cut surface. The lymphatic glands are sometimes also enlarged and hard. They are white and opaque on section from accumulation of their cellular contents.
Enlargement of the liver in rickets is not always the consequence of the pathological condition described. If a rickety child be much wasted from intestinal catarrh or other digestive trouble, the liver may be swollen from fatty infiltration. If he have been subject to repeated pulmonary catarrhs with great interference with the respiratory function, the organ may be enlarged from chronic congestion. So also turgescence of the spleen may be found unaccompanied by any appreciable lesion of the liver or lymphatic glands. In some cases the increase in size of the organ appears to be due, as in the case of the liver, to a chronic congestive process which causes a large development of hyaline fibroid material. In others the spleen seems to be the seat merely of simple hyperplasia, and presents the ordinary characters of hypertrophy, such as are seen in some cases of inherited syph ilis and in the ague cachexia. This form of enlargement is referred to elsewhere (see page 238).
The muscles have been noticed by Sir William Jenner to be small, pale, flabby, and soft. Their fibres under the microscope are softer and paler than natural, with the stripe very indistinctly marked. The brain is some times small and shrunken, so that fluid is thrown out to fill up the space left vacant in the skull cavity. It is also sometimes enlarged, so much so, in some cases, as to cause distention of the cranium. Dr. Hilton Fagge has referred to a case which was taken to be one of advanced hydrocephalus until an examination of the body after death showed that the brain filled up the cranial cavity completely. In such cases the organ, although en larged, has a healthy appearance and is of natural consistence. The hyper trophy is said to be in the neuroglia without any increase in the nerve elements.