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6. A mass of germinal matter which is endowed with powers different to those of the germinal matter from which it was derived, always originates as a new centre (nucleus or nucleolus) in pre-existing germinal matter. The origin of new centres is from within centres, or endogenously, but the mass of germinal matter which results multiplies by division.

7. During the life of every elementary part, a movement of the particles of the germinal matter takes place in a definite direction, from centre to circumference, and it is probable that by this movement of the particles from centres, the transmission of the nutrient substances in the opposite direction is ensured.

8. The relative proportions of germinal matter and formed material vary greatly in different elementary parts, in the same elementary part at different periods of its growth, and in the same tissue under different circumstances. The more rapidly growth proceeds, the larger the absolute amount of germinal matter produced in proportion to the formed material. Rapidly growing structures are soft and easily disintegrated. Firm dense tissues are of slow growth, and the hardened formed material of which they mainly consist, resists disintegration and change.

9. The pus-corpuscle is a mass of germinal matter in direct descent from the germinal matter of an elementary part. The conditions under which the growth of the germinal matter has taken place have been such as to cause its rapid increase, and to interfere with the production of formed material. For some time before perfect pus-corpuscles were produced, a tendency to the production of elementary parts, like those of the original texture, was manifested.

10. The cell-wall is not a constant structure. The definitions generally given of the cell are not applicable to the elementary parts of many tissues. Pabulum does not pass through the cell-wall to become altered by the action of the cell, but certain of its constituents are converted into germinal

matter, the living substance which becomes tissue or is changed into substances which form the constituents of secretions.

11. In the nutrition of an elementary part the following phenomena probably occur. 1. Inanimate pabulum passes through the formed material into the central portion of the spherical masses of germinal matter, while, 2. Particles previously animated move outwards. 3. The outermost particles of the germinal matter become converted into formed material. 4. A corresponding quantity of the oldest formed material is disintegrated, or the new formed material is added to that previously existing, in which case this structure increases in quantity. In nutrition, without growth, an amount of inanimate matter becomes living germinal matter within a given time, exactly corresponding to the proportion of germinal matter which undergoes conversion into formed material, and this makes up exactly for the quantity of old formed material, which being no longer fit for work, is disintegrated, converted into soluble substances, and removed.

CONNECTIVE TISSUES.

12. The connective tissues as a class cannot, by any structural characters, be separated from other tissues of the body.

13. The chief differences between a structure like epithelium (cell tissue) and cartilage or tendon (connective tissue) are these. In the first, the formed material of each elementary part is more or less separated from that of its neighbours, while in the latter the formed material is continuous throughout, but in both cases, the oldest portion of the formed material is that which is farthest from, and the youngest, that which is nearest to each mass of germinal matter.

14. White fibrous tissue and cartilage do not consist of cells, and an intercellular substance which is produced independently of cells; but the so-called intercellular substance exactly corresponds to the cell wall of an epithelial cell, and,

like this, was produced from the masses of germinal matter (cells). No 'intercellular substance' is produced independently of the living active granular substance in the 'cell,' or germinal matter.

15. The nuclei' or masses of germinal matter of tendon correspond to the 'nuclei' of an epithelial cell. The fibres of yellow elastic tissue in tendon are neither connected with, nor formed from or by, these nuclei.' The matter of the nuclei' gradually undergoes conversion into the white fibrous tissue, while new nucleus or germinal matter is produced from the pabulum.

16. The mucous tissue' of the umbilical cord is a modification of fibrous tissue. No system of communicating tubes for the circulation of nutrient juices can be demonstrated in it.

17. In certain tissues (cartilage, epithelium) the masses of germinal matter produced by division are quite separate and distinct from each other, while in others (tissue of umbilical cord, tendon, periosteum, &c.) they remain for some time connected together. Thus a thread-like or stellate arrangement may be produced, and as the several masses become further separated, the points of communication are reduced to narrow lines and often disappear altogether.

18. The osseous tissue is composed of formed material which is afterwards impregnated with calcareous matter, and corresponds to the matrix of cartilage and to the wall of an 'epithelial cell,' as for instance that of a 'cell' of cuticle.

19. The lacunæ of living bone are occupied with germinal matter (nucleus) and formed material, in which calcareous particles are still being deposited from without inwards.

20. The canaliculi are mere spaces which are left during the accumulation of calcareous matter in the formed material. Through these channels fluids pass to and from the germinal matter in the lacunæ. They are not processes which grow, but are merely channels which are left.

21. No dentinal tubes' exist in living dentine. The 'dentinal tube' like the lacuna, contains germinal matter and formed material, and the latter is gradually impregnated with calcareous matter from without inwards, that is, the oldest formed material first undergoes the process of calcification.

22. The so-called gray or gelatinous fibres are real nerve fibres, and there are many ganglia which are connected with these fibres alone. The ultimate ramifications of all nerve fibres closely resemble the gray or gelatinous fibres. These fibres are numerous in the pericardium and are distributed to all the vessels.

23. Certain forms of connective tissue may result from changes taking place in nerves and vessels. The modification of connective tissue met with in the papillæ of taste and touch, is probably, in great part, the remains of nervous structure which is incapable of being removed by absorption. Certain forms of connective tissue are produced by germinal matter but some varieties consist of the remains of structures which were active at an earlier period of life.

24. In some situations in which areolar tissue corpuscles' are said to exist, and to form a special system of tubes and cells connected with the distribution of nutrient juices, the following bodies may be recognized; nuclei of nerves, nuclei of capillaries, nuclei of white fibrous tissue, nuclei of yellow fibrous tissue, nuclei of fat cells, lymph, and white blood-corpuscles. Each of these masses of germinal matter is connected with the production of its own peculiar tissue or formed material, and there are no cells and tubes to be demonstrated which are concerned in the distribution of nutrient matter to these textures. The nutrient fluid permeates the tissue generally, and each mass of germinal matter selects its proper pabulum and undergoes increase, while the older particles undergo conversion into tissue.

EXPLANATION OF THE PLATES.

With the exception of the figures 13, 14, 15, 16, 17, 18, Plate III, which are mere diagrams, the drawings represented in the following Plates are actual copies from nature and are as faithful as I could make them. They have all been drawn to a scale, and are represented the actual size they appeared. In most cases the specimens have been preserved, and can be seen by any one who desires to examine them (see preface). Each specimen was drawn on wood by myself, and with very few exceptions, the engraver has carefully preserved the lines I have drawn.

PLATE I.

To illustrate the structure of the pocket microscope which is represented mounted on its stand in fig. 2, page 27.

*

Fig. 1. The microscope, half the real size. It consists of three tubes a, b, c; a carries the eye-piece, is four and a-half inches long, and slides in 6 which is the same length, but only slides up to its centre in the outer tube c. Tube b carries the object-glass, points to a bolt which can be fixed by aid of a rack and tooth, at any height, according to the focal length of the object-glass. This arrangement prevents the risk of the object-glass being forced through the preparation while focussing. At the lower part of the body are seen, the screw for fixing the preparation in any position, the aperture for throwing the light on opaque objects, and part of the spring which keeps the preparation in contact with the flat surface below, while the requisite movements of the preparation are made with the hand.

Fig. 2. A modification of the instrument represented in

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