378 PATHOLOGY membrane of the stomach and intestine the surface-moisture amounts to a definite layer of glairy or tenacious mucus. In some of the mucous membranes, such as those of the pharynx and oesophagus, trachea and bronchi, there are distinct racemose glands which appear to subserve solely the purpose of lubricating or keeping moist. In every case the normal mucus of an epithelial surface may be taken to be a product of the epithelial cells ; it is as if it were a common and rudimentary function of surface-epithelium anterior to the specific secretions of organs. It is in this common and rudimentary function that the catarrhal process has its roots, a process which not only exceeds the physiological limits of sur face-moisture, but may even throw into the shade the specific secretion of the part or organ. The catarrhal secretion is always characterized by the large preponderance of cells, and the propor tion of cellular elements increases as the mucous substance becomes muco-puruleut and purulent. It is important to observe that there is no definite line where the limits of normal moistness end and "inflammation" begins ; and, as it is desirable to put off as long as possible the introduction of that entity into pathology, we shall best proceed in the study of catarrh by advancing from the physio logical activities of cells. The ca- Nature of the CatarrJuil Process. The catarrhal process, like all tarrhal the so-called inflammatory processes, has been rendered ambiguous process, by the undoubted share in it that is taken by hyperamiia or afflux of blood to the particular epithelial region. By some the hyper- rcmia has been taken to be the primary fact, the increased rush of blood to the part and the local stagnation of the same being traced to an upset of the controlling and equalising nervous mechanism of the vessels and to alteration of their walls ; by others the local cellular process has been regarded as determining the afflux of blood, as if by a kind of attraction. Whether the afflux of blood precedes the unusual activity of the epithelial cells, and whether some of the catarrhal cells may not be emigrated colour less corpuscles, are questions that may be considered open ; but there can be no question that catarrh is essentially a hypersecre- tion of the epithelium, or the secretory activity so modified that it becomes to a great extent formative, or its product to a great extent cellular. The difficulty of proving this is owing to the fact that the normal production of mucus from epithelium is a very subtle and rapid process, the morphological phases of which are hardly to be detected ; in this respect it must be considered analogous to the formation of red blood -disks from hrematoblasts. And, as the details of the luematoblastic process are best seen in certain abnormal manifestations of it, and even in those cases where the morbid condition is one of anremia, so the complete physiological paradigm of mucus-production is best seen where there has been some interference with the perfection of function. We shall per haps not go wide of the mark if we describe the catarrhal process as a reversion to a more embryonic or more elementary type of cellular activity. The higher the type of secretion, the less obvious are the morphological changes in the secreting cell ; in an organ like the liver, which had been early acquired in the evolution of the animal body, the secretion has become so elaborated in the higher animals that the steps of it present hardly any morphologi cal features at all ; on the other hand, in an organ like the breast, which is a late (mammalian) acquisition, the changes in the secret ing cell can be followed at leisure. Catarrh in any mucous surface is the same primitive kind of secretion, and it may be said, in a word, to consist of a fluid product and of an additional by-product of cells. The original epithelial cell is detached bodily, nucleus and all ; the protoplasm becomes the more or less viscid or semi fluid part of the mucus ; and the nucleus goes with it as the catarrhal cell. The more the cellular elements predominate, the farther does the secretion deviate from the normal, until we reach the limit of pus, where we invoke the entity of "inflammation." Catar- Succulence and Thickening of the Catarrhal Mucous Membrane. rhal infil- A mucous membrane which has been the subject of catarrh for tration. some considerable time becomes thicker and more succulent. If it be examined in microscopic sections it will be found that the underlying connective tissue has become involved ; the tissue is "infiltrated "with round nuclearcells (fig.42); the fibres are becoming ^B^N!!&*V - -*fjfe> t =* FIG. 42. Epithelial surface and subrnucous tissue in a state of catarrh (tubular gland of the dog s skin), a, a , collections of catarrhal cells in the epithelial layer ; 6, the same in the underlying connective tissue. thicker ; and the fineness, delicacy, and translucency of the tissue are disappearing. At certain spots where the "infiltration " and asso ciated changes are greatest the surface breaks or ulcerates, and a "catarrhal ulcer" remains. The central fact in this process is the infiltration of the round nuclear cells beneath the epithelial surface. The facile way of accounting for them is to assume that the colour less corpuscles of the blood had escaped through the walls of the small veins ; but it is more in accordance with observed facts and with unambiguous analogies to regard them as catarrhal cells which have found their way into the depths of the tissue instead of flowing off by the surface. The presence of these cells in the spaces of the connective tissue is not without effect on that tissue itself ; they rouse it to a formative activity which conducts to the succulence and thickening of the mucous membrane, and, it may be, to ulcera- tion at particular spots. To enter on this subject at present would be to open up the question of the infective action of one kind of cell upon cells of another kind (see pp. 382, 383). Physiological Analogies of Catarrhal Infiltration. The infiltration of catarrhal cells beneath the mucous surface has close analogies in the normal processes of the body. It is exactly paralleled in one of those crude forms of secretion to which the catarrhal pro cess has been compared, namely, the kind of secretion, gradually rising in intensity, which goes on in the breast during the period of gestation. This process can be most conveniently observed in the mamma of the cat or dog, where the crude secretory products are for a time cells of considerable size filled with yellow or brown pigment ; the pigmented cells can be followed from the secreting structure into the spaces of the surrounding connective tissue, and thence into lymphatic glands. It would not be carrying this analogy too far to regard the lymphatic follicles of the mucous membranes as collections of or receptacles for the cellular by-pro ducts of the mucous secretion ; such are the tonsils, the follicles on the back of the tongue and pharynx, the lymphatic follicles of the stomach of some animals (but not of man, unless it be in infancy), the extensive stratum of lymphoid cells in the villi of the small intestine and the more definite collections of the same (Peyer s patches), and the lymphatic follicles of the great intestine. Certain it is that all these collections of round nuclear cells are subject to very considerable increase when there is catarrh in the corresponding mucous surface. Not only so, but in catarrh they will show themselves prominently even where they are hardly known to exist normally ; thus, in the intestinal catarrh (summer diarrhoea) of young children, even the thin folds of the mucous membrane (valvulse conniventes) will be found studded with round nodular or somewhat flattened lymphatic follicles. In intense catarrh these follicles are the favourite seats of ulceration, their substance changing into a "follicular ulcer." In other cases the catarrhal process makes its influence felt in the nearest lymphatic glands, which may be regarded as the second line of receptacles for the by-products of secretion (as well as for the matters of absorption), the submucous follicles being the first line ; and, under these circumstances, the lymphatic glands may even suppurate (as in the axillary lymph-glands of the breast after weaning). Tumour-diseases of Mucous Membranes and of Secreting Structures Tumoi generally. If catarrh of mucous membranes enters, as Rindfleisch diseast says, into the larger half of all the morbid conditions to which of epi- marikind is subject, the tumour-diseases of the epitheliated surfaces tlieliat and organs may be said to rank among the most formidable of all surfaci maladies, inasmuch as they include, cancer. Cancers are diseases primarily of mucous membranes and other secreting structures, most commonly of the stomach, next to it of the uterus, of the female breast, and of the intestine ; another variety of cancers (epithelioma) is diseases of modified epithelial surfaces, namely, the skin in general, and the lip and tongue. There are, however, much simpler tumour-disorders of epitheliated surfaces which it will be convenient to take first. Warts (Pajnllomata). Papillomata of the moist epitheliated Warts surfaces are found almost exclusively in those situations where there is a transition from skin to mucous membrane. The rule may not be universal, but there are many instances in which these wart-like growths have an undoubted relation to a catarrhal pro cess of the surface, where the removal of the catarrhal products has been interfered with. One of the most striking illustra tions of this law occurs in veterinary practice ; in the horse, especially when he is overworked and ill cared for, the natural smegma of the prepuce gets retained, owing to the fixity of the sheath ; the accumulation has more than a mechanical effect, for it appears to induce a papillomatous condition sometimes of the whole mucous surface. The papillomata are new growths, either in a broad layer of the uniform thickness of a quarter of an inch or more, or they r are large dendriform masses arising at various points and each attached by a narrow stem. It is hardly a catarrhal process that we have here to deal with, but it is none the less a disorder of secretion. The natural secretion not finding an outlet, the secreting surface adapts itself gradually to the unusual conditions. The surface becomes ridged or thrown into folds, or papilla? arise at isolated points ; blood-vessels run in the central parts of all these reduplica tions of the membrane ; and the epithelium, instead of disengaging itself in successive generations of cells after the manner of the natural smegma, takes on a formative activity and builds up an
