(4.) The compound granuk-corpuscle (com pound inflammation-globule; Gluge) does not occur in large numbers in pus ; many drops may be examined without a single one pre senting itself. This corpuscle is of spherical, and slightly irregular, form, ranging from TArcr to T.?" of an inch in diameter (fig.
92) ; and composed essentially of granules and an involucrum. The involucrum is not di,,solved by water, and s'mply rendered trans parent by acetic acid ; the granules vary from ten, to twenty or thirty, or even many more in number. Occasionally the action of' acetic acid discloses a single, double, or multiple nucleus lyin. close to the involucrum. The granules arelikewise kept in situ by a fluid of thickish consistence, in which, if few in num ber, they may be seen to move. The course of formation of these corpuscles seems to be, agglomeration of granules from exudation matter, investment with a membranous wall, production of a nucleus.
Fat occurs invariably in more or less quan tity in pus, and exhibits itself under the micro scope, under the forms of molecular granules, as above referred to; oil globules ; crystals of cholesterin.
Saline crystals occasionally occur in pus, especially in certain unhealthy varieties of the fluid. When they exist, some peculiar cir cumstances have probably caused unusually rapid, or otherwise modified, evaporation of the liquor puris.
Infusoria (monads and vibrions, especially the vibrio lineola) occur in pus : we are un able to affirm whether their presence is always an evidence of decomposition in the pus itself. The attempt, made by Gruithuisen, to dis tinguish various fluids by the characters of the infusoria developed within them, has not led to any satisfactory results.
Pus, when recent and healthy, has a slightly alkaline reaction ; we have known it neutral, however, in cases where there was no reason to believe any chemical change had occurred. It readily becomes acid from the development of an acid — the lactic it is supposed : the change from one to the other reaction, evi dently depends, in some cases, on a primary change in the constitution of the pus at the moment of generation ; for we have found pus from the same wound, sometimes alkaline, sometimes acid, though taking all precautions to ensure its examination at the moment of production.
The published analyses of pus are extremely numerous. Among the most recent and care fully conducted are several by. Dr. Wright if, of which the following may be selected as specimens ; it is clear that the chemical con stitution of the fluid must vary somewhat with the locality from which it has been de rived, inasmuch as pus can very rarely be obtained free from minute quantities of the textures or secretions in connection with which its production has occurred.
Some of the discrepancies in the results given by various experimentalists, doubtless depend in no small degree on the differences in the manner of conducting their analyses. Making allowance for these sources of error, it may be inferred that liquor puris consists of water varying in proportion from 76 (Von Bibra), and 82 (Dumas), to 90 (Lassaigne, Pearson, and Von Bibra #) per 100, of dis solved albumen, of fibrin, fat, and extractive matters. A peculiar principle (precipitable by acetic acid and by alum) has been assigned to pus, under the name of pyin, by Giiterbock : that such a special substance exists independ ently of the means employed to procure it, has been questioned or denied by Valentin, Dr.
John Davy and others. At the present hour the real presence in pus of the principle, described under this name, is admitted by chemists ; it is said (probably- pro tempore) to be tritoxide of protein. Glutin is enumerated by Martins among the constituents of the pus of empyema ; its existence must be an exceptional occurrence. Phosphoric, hydro chloric, and lactic acids in union with lime, potassa, soda, magnesia, and ammonia, form the ordinary saline elements of the fluid. Oxide of iron, though put forward as a constant in gredient by Cruickshank, Koch, Krauss, Gael (in the horse), Pearson, and Giiterbock, is in all probability only present in instances of ac cidental admixture of blood.
The micro-chemical properties of the pus corpuscle are important. Pure water exercises no obvious influence on it for days, even, ex cept that of rendering the nucleus more visible, and slightly increasing its size by passing through the cell-wall by imbibition. Saturated sugar-water, blood, mucus, and saliva, unless (as observed by Henle) the latter be acid, produce scarcely any alteration in the cor puscle. Urine gives it an extreniely ragged outline in the course of a few days (earlier if' it be alkaline), and eventually breaks it up completely. Alcohol slightly corrugates, with out dissolving it. Under the action of acetic acid the corpuscle loses its granular appear ance, commonly undergoes a change of bulk ; and the distinct outline of the involucrum fades away, while the nucleus, simple or com pound, becomes clear and distinct. What is the nature of these changes ? The removal of the granular aspect of the corpuscle is not readily explained. We were at one time dis posed to regard it as produced by the simple unfolding of the involucrum, caused in turn by imbibition of the fluid re-agent, — believ ing that the granular appearance arose simply from a corrugated state of the surface of the involucrum. But the uniformity of the gra nular appearance, its constancy of occurrence, its extreme delicacy, and the fact that it is not removed altogether, no matter how dis tinctly the corpuscle be swollen by imbibition, appear to throw doubt upon this view, and render it more probable, if not actually cer tain, that it depends on the presence of mo lecular matter within the involucrum ; — the change of bulk is sometimes one of increase, sometimes one of decrease, — a difference which has appeared to us traceable to the varying degrees of dilution of the acid. That the involucrum fades simply, without being, as was at one time supposed, destroyed, is commonly obvious on simple inspection ; it appears as a sort of thin, transparent halo round the nuclei. But, were there any doubt, this would be removed by the addition of solution of iodine*, which restores the clear definition of the cell-wall. The fading of the involucrum is, however, an early stage of so lution ; for, if much acid be added, the halo disappears and cannot be restored. In re spect of this disclosure of the nucleus three opinions have found their supporters : (rt.) that a simple or compound nucleus, pre-exist ing in either form, is simply rendered visible by the acid ; (b.) that it is exposed and, be sides, split up into parts; (c.) that it is an ap pearance altogether produced by the acid. That the first of these opinions is the correct one, appears (if on no other grounds) from what has been said in a previous page on the discovery of the nucleus in recent unchanged pus.