in young animals there is less than in old animals. In creatures of the simplest organization, whose tissues are, so to say, embryonic throughout the whole period of their existence, there is none. In the higher animals whose tissues pass through so many phases before they attain their perfect form, there is a large quantity. A form of connective or areolar tissue is the result of certain degenerative processes occurring in higher tissues. It may result from changes occurring in vessels, nerves, and muscles. In various glandular organs which have undergone degeneration, a form of fibrous tissue remains behind. In cirrhosis of the liver, I believe the fibrous matter which is present results not from the effusion and fibrillation of lymph, but is simply the remains of the degenerated capillaries and ducts. In livers in this condition, vessels and shrunken secreting structure, can always be demonstrated in the substance of the so-called fibrous tissue. The same

remarks also apply to the kidney in certain cases of disease, and to other glandular organs. The structure of inflammatory lymph has been already described. This gradually undergoes a process of condensation and a form of fibrous tissue at last results.

I must now make a few remarks upon certain fallacious appearances which may be produced by the mode of preparing specimens of healthy tissues, and which may easily be mistaken for fibrous tissue. I have already adverted to this matter in my first lecture; I have seen the smaller blood-vessels, both arteries and veins, stretched in one part of their course so that the transparent injection was pressed out of the transparent tube, while its continuity with the other parts containing the blue injection was perfectly certain. Had I seen the stretched portion alone, I should have affirmed most positively that it was a form of areolar tissue, and the nuclei which belonged to the structure forming the coats of the vessels might have been considered to be the nuclei of the areolar tissue.

Delicate nerve fibres when stretched and pressed could not

be distinguished from connective tissue. Under the same circumstances, capillary vessels and the membranous walls of ducts may be set down as ́areolar or connective tissue.' It would seem, then, that there are―

1. Certain forms both of white and yellow fibrous tissue which are produced directly from germinal matter as other tissues, and in which masses of germinal matter may be demonstrated at every period of life.

2. Certain forms which may be regarded as the residue of higher tissues which have ceased to discharge active functions.

3. Certain forms of fibrous tissue (indefinite connective tissue), as in the papillæ of touch and taste, which result from changes having occurred in the terminal branches of the nerve fibres.

4. Certain forms of fibrous tissue, resulting from degeneration occurring in the course of disease (abnormal).

5. An appearance of fibrous tissue produced by pressure, crumpling, and stretching of nerves, capillaries, and other tissues.

You will have gathered from the observations I made when the last preparations were sent round, that I consider, for instance, in a structure like skin, that a number of bodies, taking part in the formation of special tissues, have been dismissed under the term 'connective tissue corpuscles.' The following bodies, composed of germinal matter and generally termed nuclei, are certainly present:-1. Nuclei of nerves. 2. Nuclei of capillaries. 3. Nuclei of white fibrous tissue. 4. Nuclei of yellow fibrous tissue. 5. Nuclei of fat cells. 6. Lymph, and white blood, corpuscles. In certain papillæ all the nuclei present may be shown to belong to nerves and capillary vessels, and between the elementary muscular fibres of the young mouse this is also strictly true. I do not think that in such situations there are any corpuscles which could properly be called areolar tissue corpuscles, nor have I succeeded in obtaining any facts which would favour the view that there

are corpuscles of any kind distinct from the cells' or 'nuclei' (germinal matter) of the tissue, which perform special offices connected with the nutrition of these higher tissues.

I have troubled you with much detail with reference to the anatomy of the connective tissues; detail which, I fear, must have been to many almost devoid of interest, but as my conclusions are greatly opposed to those of many high authorities, it was necessary for me to go somewhat minutely into the question, and I naturally felt bound to bring forward some of the facts I have obtained in favour of the view I have been led to adopt.

Let me, in conclusion, thank you for the warm encouragement you have afforded me in taking so deep an interest in the questions I have ventured to bring under your consideration. I desire, too, particularly to acknowledge the kindness of the President in permitting me to give a course of lectures in this College-which possesses associations of the deepest interest to every one who delights in prosecuting anatomical research.

M

GENERAL REMARKS AND SUMMARY OF

CONCLUSIONS.

In this course of lectures I have endeavoured to prove that the changes which more especially distinguish living structures from lifeless matter, take place in the substance I have termed germinal matter and in this alone. The particles of which this is composed after passing through certain definite stages of existence, undergo conversion into the peculiar substance or substances they were destined to produce. It is the germinal matter alone which is capable of forming, producing and converting. The matter external to it (cell wall, intercellular substance or fluid) has been formed or produced, and it may be changed, but it has no power to produce structure or to alter itself.

There are many objections to the use of the term 'cell' as indicating the elementary unit of structure. The cell-wall is not constant although it is absolutely necessary to the existence and action of the 'cell,' that is, in the sense in which this word is ordinarily used. There are comparatively few instances in which a true vesicle exists at all.

Every living structure, and every elementary part that is living, is composed of matter which is forming and matter which is formed—germinal matter and formed material. The term cell is short and convenient and if the definition usually given were modified, I think it would possess advantages over the term 'elementary part.' We might give the word a

much more general signification and say that a 'cell' is composed of matter in two states which I have described under the terms germinal matter and formed material.

It appeared to me that great confusion would have resulted if I had attempted to show when describing various structures the exact parts which according to the ordinary nomenclature corresponded to my 'germinal matter' and 'formed material' and I have therefore purposely omitted to discuss the question at all in detail. It may, however, be well to state now that in some cases the germinal matter corresponds to the nucleus, in others to the nucleus and cell-contents,' in others to the matter lying between the 'cell-wall,' and certain of the cellcontents;' while the formed material, in some cases corresponds exactly to the 'cell-wall' only, in others to the 'cellwall and part of the cell-contents,' in others to the 'intercellular substance,' and in other instances to the fluid or viscid material which separates the several 'cells, nuclei or corpuscles,' from each other. It may be remarked—

That the nucleus' of the frog's blood-corpuscle is germinal matter; the external red portion (cell-wall and coloured contents), formed material.

That the white blood corpuscle, the lymph and chyle corpuscle, and the pus and mucous corpuscle, are composed entirely of germinal matter, with a very thin layer of formed material; the viscid matter or mucus between the mucous corpuscles is formed material.

That the nucleus' of an epithelial cell of mucous membrane, or of the cuticle is germinal matter; in a fully formed 'cell' the outer part, cell-wall and cell-contents' consists of formed material.

That the cell-wall' of a fat-cell or of a starch-holdingcell is formed material; the nucleus' of the former, and the ''primordial utricle' of the latter, are germinal matter; while the fat and the starch are the secondary deposits produced by