176 MR. TOYNBEE ON THE ORGANIZATION AND NUTRITION 



ternal fibrous capsule of the intervertebral substance is firm and dense. Its circum- 

 ference is almost wholly composed of fibrous tissue arranged in circles, between 

 which circles are rows of cartilaginous corpuscles. Nearer to the centre, the fibrous 

 tissue is found to consist of distinct circular bands, separated from each other by 

 large masses of corpuscles, and more centrally still the fibrous tissue is laxer, and 

 the cells which are scattered through its meshes are larger and more abundant. 



I shall now give an account of my examination of the intervertebral substance of 

 the human subject at various periods of development. 



a. In the human foetus of the third month the intervertebral substance of the second 

 and third lumbar vertebrae is firm and white at its circumference, soft, and of a leaden 

 hue towards its centre. The central part is composed of numerous cells or corpuscles, 

 some being round, others stellated. It also presents large masses of other cells 

 aggregated together, and somewhat of a darker colour. Nearer to the circumference 

 of the intervertebral substance the cells are arranged in distinct lines, and at its cir- 

 cumference they are elongated at each extremity, and so attenuated as to assume the 

 appearance of fibres. 



h. In a human foetus of seven months the intervertebral substance is composed of the 

 external fibrous and the central cartilaginous portions. The central portion is almost 

 entirely composed of distinct round cells, which are found, on being traced towards 

 the fibrous part, to become more elongated at their extremities, and to form, as it 

 were, series of fibres. The fibrous portion is made up of circular layers of fibres, be- 

 tween which cells are interspersed. 



c. In a human foetus of nine months the central part of the intervertebral substance 

 is soft, and is composed of cells, and of an intercellular substance. The external 

 fibrous portion is distinct, and is interspersed with cells. 



d. From the period of birth to adult age, the change undergone by the intervertebral 

 substance, consists in the gradual encroachment of the fibrous portion upon the car- 

 tilaginous. 



e. In adult age the central portion still continues to present corpuscles, although not 

 in so great a number. They are always found interspersed through a gelatinous 

 mass. The external fibrous portion also presents corpuscles between its circles of 

 fibrous tissue. 



f. In old age the corpuscles of the intervertebral substance are less numerous than 

 in the adult. The fibrous tissue is also more dense and unyielding. 



2. The fibro-cartilages, comprising those of the symphysis pubis, and of the sacro- 

 iliac articulation also, consist of an external fibrous portion, and of a central cartila- 

 ginous one, which undergo the same relative changes, as age advances, as the fibro- 

 cartilages just described. 



Of the Structure of the Second Class of Fibro-Cartilages. — I have made careful ex- 

 aminations of all the inter-articular fLhro-csLvtilages at several periods of their develop- 

 ment and growth, and the following is the result of my inquiries concerning their 



