Now the question arises: Does the inner contour represent that delicate shade, which I described on the fresh unaltered bloodcorpuscle as representing the inclination, passing from its thick convex marginal to its thin and concave central portion; or is it in reality the inner contour of an existing membraneous layer, made visible by the solution of the protoplasm within it, as in the case of those large nucleated coloured blood-corpuscles of the Amphibia? Let us try to solve this question. A close examination of the front surface of one of these blood-corpuscles, affected by the action of the water, will reveal that the diameter of the central portion of the corpuscle has increased, while that of the peripheral portion, representing its convexity, appears much narrower than in the fresh specimen. From this we may judge that there must have been some loss of substance in the interior of the blood-corpuscle, causing it to collapse in thickness. In other words, the protoplasm, with the exception of a thin stratum or layer forming the surface of the corpuscle, was dissolved by the action of the water, giving to the whole the character of a cell. Thus the changes brought about by the action of water in the non-nucleated bloodcorpuscles of Man are similar to those observed under the same conditions in the large nucleated corpuscles of the Amphibia. No true cell-membrane can be discovered in their normal condition; while in either case a delicate stratum seems to exist at the surface of the corpuscle, which, being denser in its nature than the rest of the protoplasm, resists longer the solvent action of the water, and in consequence manifests itself in the form of a delicate double contour. In the human blood-corpuscle this membraneous layer, as we have called it before, must be exceedingly delicate, as no trace of it can be discovered on the fresh unaltered specimen. It is probable, however, that its invisibility in the fresh condition is owing to the circumstance of the peripheral portion or margin of the human blood-corpuscle being perfectly rounded, while the margin of the blood-corpuscle of the Amphibia is almost flat, and proportionately thinner, in consequence of the bi-convexity of the whole disk.

But the fact that a cavity is produced in the interior of the blood-corpuscle by the action of water, is rendered still more apparent when a specimen is examined in its exact profile, as may be seen in Fig. 62, b, where the delicate median line represents the cavity. This can only be done while the corpuscle is floating in the water, and slowly turning around its horizontal axis. When the corpuscles, after being altered by the action of water, are treated with a weak solution of chromic acid, the double contour appears still more distinct.

The blood-corpuscles of Man do not swell or assume a spherical form (as I myself several years ago erroneously believed) by the

action of water; but, on the contrary, with the exception of a very slight diminution in size, they preserve the exact form, whether normal or distorted, which they possessed before the application of the water. Nevertheless, if the water be applied immediately after the various changes of form have taken place, they resume their original shape, as I have observed.

The presence of a delicate membraneous layer may be furthermore demonstrated by a simple experiment on the fresh bloodcorpuscles, and without the assistance of any reagent. I cannot forbear to recommend this experiment, particularly to those histologists who deny the existence of this layer, in order to convince them of their error. It is as follows:-A very small drop of human blood, about the size of a small pin's head, is taken and placed upon the glass slide. After being covered with a small round covering glass, this is firmly pressed down upon the blood by means of the point of a forceps, with the object of compressing or crushing the blood-corpuscles as far as possible. For this reason, the point of the instrument may be passed over the covering glass, for the purpose of applying the pressure to every part of the blood; or the blood may be rubbed between the two glasses until they adhere to each other. A subsequent microscopical examination will show that it is not an easy matter to crush these bodies into a homogeneous mass, though they may in some places, where they formed small masses, have apparently run into each other. In directing our attention to single individuals, we find that they have considerably increased in their dimensions by having been pressed perfectly flat. Every trace of their central concavities and peripheral convexities, indicated in their normal condition by their light centres and by their bright margins, has disappeared; their bodies are uniform in colour or shaded throughout, with the exception of a light greenish border, similar or even more distinct than that seen on the coloured blood-corpuscles of the Amphiuma or Frog. On some of them clear streaks, representing fissures, caused by a rupture of the membraneous layer are observed. Those blood-corpuscles which had assumed the mulberry or thorn-apple form before the pressure was applied, also will be found pressed perfectly flat, with their dimensions increased and their margins crenated. The same light greenish border, mentioned before, will also characterize in these instances the margins of the blood-corpuscles. Some corpuscles have preserved their form of a circle, while the outlines of others appear more or less irregular, as kidney-shaped, ellipsoidal, spindle-formed, &c., in accordance with the form which they possessed before the application of the pressure; or when pressed into a mass, according to the degree of the mutual pressure exerted upon each other. If now a group or small mass of blood-corpuscles in the prepara

tion is carefully examined with a first-class objective of sufficient amplification, it will be found that they have not run into each other, but that, on the contrary, the outlines of almost every individual may be discerned, however distorted they may be.

As in this experiment the blood-corpuscles are pressed completely flat, they represent minute plates with level surfaces, through which the rays of light pass without undergoing much or any refraction, except in places where a difference in the properties of their substance might exist. But, as the membraneous layer is probably somewhat differentiated from the rest of the body, it is seen at the margin of the blood-corpuscle in the form of a light greenish border. By applying a drop of water to the preparation before it has become dry, the blood - corpuscles are gradually rendered pale and faint; and their greenish borders will now appear in the form of distinct delicate double contours, as described before. In proportion to the amount of pressure previously sustained, they will retain their dimensions and their flatness; and in those places where they were crowded before the application of pressure, whether mutual or by the covering glass, and in consequence much distorted in shape, they will be seen separating from each other as the water takes effect, and floating away, presenting the same appearances as the others described.

In the course of my investigations into the structure of the coloured blood-corpuscles of Man, I also studied the effect of various reagents, such as chloroform, acetic, nitric, and carbolic acids, alcohol, as well as solutions of hydrate of chloral, boracic and chromic acids, &c., either in the gaseous or liquid form, upon these bodies. The changes observed to take place on these corpuscles by the action of these agents are, though not in every instance exactly alike, yet similar to those we have seen to occur on the blood-corpuscles of the Amphiuma or the Frog; they mainly consist in the escape or destruction of the hæmoglobin, contraction or coagulation of the protoplasm, change of form, &c. As I have described them before in connection with the bloodcorpuscles of these Amphibia, they require no further remarks for our special purpose, except that they all appear to corroborate my view of the simplicity of the structure of the non-nucleated coloured blood-corpuscle, as well as of that of the nucleated.

In concluding this treatise on the structure of the coloured blood-corpuscles, I have only to add that I still believe a part of their function to be secretory. In accordance with this view I regard them as true glandular cells, which, independent of the part they may act in the transfer of ozone, are also engaged in appropriating certain materials from the plasma of the blood, in order to transform them into other bodies by virtue of their secretory power, and to finally return them to that fluid in the special

condition required for the subservience of other purposes, such as the preservation of the normal constitution of the blood, as well as the nutrition of the various tissues.

Changes in the substance and form of the coloured bloodcorpuscles of Man, similar to those above described, and which may be detected by the aid of the microscope, occur in various pathological conditions of the system. Although some attempts have been made by several pathologists to study these changes, no definite results have to my knowledge hitherto been obtained. The cause of this seeming failure, however, evidently depends on the difficulty attending the investigation of this subject, and I entertain no doubt as to the final success of these studies, if conscientiously and steadily pursued. For a number of years I have occasionally directed my attention to this subject, and have become convinced that changes in the form and character of the coloured bloodcorpuscles of Man, which may be detected by microscopical examination, do occur in pathological states of the system; but as my observations were confined to only a few diseases, as yellow fever and rheumatism, and were not made systematically, I shall forbear entering upon this subject at present. After I shall have accumulated additional facts to those already obtained, and on a more extended scale, I hope to present them in proper form to the profession.

II.-On the Present Condition of Microscopy in England.
By FRANK CRISP, LL.B., B.A., Sec. R.M.S.

(Read before the ROYAL MICROSCOPICAL SOCIETY, April 3, 1878.) My object this evening (writing throughout in the spirit of the Publican and not of the Pharisee) is to call attention to what I think is an indisputable fact, that in recent years no substantial progress has been made in this country either in the knowledge of the theoretical principles of the microscope itself, or in the systematic investigation of microscopical phenomena.

The microscope has, in fact, come to be regarded merely as the tool of the naturalist and the histologist; and notwithstanding the objects for which this Society was established, it may, I think, be truly said that out of the entire scientific world there is probably no body of men who devote so little real attention to the principles that lie at the root of that branch of science of which they are disciples, as do the English microscopists.

As a particular instance, I may refer to the apathy that has been shown in regard to the researches of Professor Abbe on the theory of the microscope, researches undoubtedly as important as any that can be found in the whole of its history, and rivalling even the discovery of achromatism, or that of Lister on aplanatic foci. It is, I think, not a little humiliating that such a discovery -in one aspect so simple-should not have originated in this country, we being the first, and for many years the only, nation to maintain a "Microscopical" Society.

Whatever may be the cause of such apathy, it is evident that it cannot be attributed to any deficiency in the power of perseverance; for when we enter upon the discussion of a question, say of angular aperture, we do not rest content until a point has been reached which renders it impossible for anyone to say that the subject has not been exhausted to the very last limits.

For this the condition of our literature is in part answerable. Recall the contents of the generality of modern English treatises on the microscope, and what do we find? Out of a given number of pages, a very small portion only is devoted to the optical prin

The statement of the "Objects of the Society," prefixed to the Charter and Bye-laws, sets forth that "the Society was established for the promotion and diffusion of improvements in the optical and mechanical construction, and in the mode of application, of the microscope:

"For the communication and discussion of observations and discoveries tending to such improvements or relating to subjects of microscopical observation :

"For the exhibition of new or interesting microscopical objects and preparations, and for the formation of an arranged collection of such objects:

"For affording the opportunity and means of submitting difficult and obscure microscopical phenomena to the test of instruments of different powers and constructions:"For the establishment of a library of standard microscopical works.”