k. Medullary sarcoma.—Another form of tu bercle, associated with the cancerous diathesis and belonging to the carcinomatous family, is medullary sarcoma, or encephalosis. The tu mours produced by this disease are larger than scrofulous tubercles, and more regular in form and fewer in number than scirrhous tumours. Developed originally in the same way with scirrhus, by infiltration into the tissue of the lobules, or into the vessels themselves, of the peculiar greyish white and opaque substance of which they are composed, they increase in size and obstruct the circulation in the surrounding lobules. Their internal structure is a loose cellular base, filled with a soft and brain-like matter, frequently coloured with blood, or containing coagula in various stages of soften ing, resulting from limmarrhagic extravasation.
Sometimes these tumours present a certain de gree of consistence, but as they increase in size they become more and more softened and pulpy. Baillie describes a large tumour in the liver which he considers scrofulous from being softened in the centre, and containing a fluid resembling pus; this is most probably a tumour of the kind I am now describing. Another tumour, of which lie expresses himself at a loss to understand the nature, soft, of a brownish colour, and of about the size of a nut, appears to be also referable to the same species.
The second and third varieties of the tubera diffusa of Farre present characters resembling this disease. V. 2. " Tubera, elevated at the surfaces of the affected organ, encysted, or having dis tinct cells, formed by the growth of a fungus, which separates in flakes, and is composed of a fine reticular texture, containing an opaque white fluid." V. 3. " Tumours rising with a regular swell from the surfaces of the affected parts and yielding to the touch, composed of a very delicate reticular texture, pulpy in its consistence, varying in its colour even in the same subject, charged with an opaque fluid, and growing from cysts or cells." Cruveilhier considers the venous capillary system as the seat of origin of carcinoma, par ticularly of the form which I am now consi dering ; hence he observes, " Ayant exprime dune coupe faite a un foie cancereux une ma tiere d'un blane-rougeatre, encephaloide qui se moulait It la manure du vermicelle, et qui pouvait acquerir en se tordant one grande lon gueur, j'apercus sur cette coupe tin orifice plus considerable que les autres; j iucisai cet orifice et je parvins dans un vaisseau tres volumineux qui me parut etre une des ramifications de la veine porte. Alors je dissequai avec beaucoup d'attention cette veine, et je ne fus pas peu etonne de voir que cette veine, depuis les plus grandes jusq'aux plus petites divisions, etait remplie par cette matiere encephaloide, adhe route aux parois et tout-a-fait semblable it celle qu'on exprimait par les coupes faites au foie. 11 me fin facile de suivrc les ramifications ex tremement dilatees de la veine jusque dans l'areoles des coupes. L'alteration etait born&
it la veine porte, les veines hepatiques et leurs ramifications etaient parfaitement saines." 1. Fungus hiernatodes is the term applied to all carcinomatous tumours which have a ten dency to the unnatural development of new vessels and to effusions of blood into their tissue. In the same organ, hard and cartilaginous scirrhous tumours may exist with those of a softer texture, and of a medullary form, and both of these may be mingled together in the soft, elastic, and bleeding mass which consti tutes fungus hmmatodes. The tumours of fungus limmatodes are often of very large size, and by their frequent hemorrhagies give rise to extreme symptoms and the speedy death of the patient. Farre arranges this form of carcinoma among his tubera diffusa, of which it forms the fourth variety, which he thus defines : " Tu mours elevated at the surfaces of the liver and inclining to a round figure ; pulpy in their con sistence, being charged with a thick and opaque fluid, variegated in their colour, chiefly white mingled with red, the former prevailing in their incipient, the latter in their advanced stages, composed of a very vascular and reticular tex ture, attached either to distinct pouches or to the substance of the liver, and so unlimited and rapid in its growth as to burst or destroy the peritoneal tunic of this organ and to pro trude in the form of a bleeding fungus." rn. .111elanosis.—Melanosis exists in the liver, as in other structures of the body, 1st, as a melanic secretion infiltrating the cellular stric ture of the organ, and giving a diffused general blackness to the substance of the lobules; 2d, as a morbid tissue composed of an areolar cel lular network, in which the black carbonaceous matter is deposited ; or 3dly, as a melanic pigment accompanying carcinoma or tubercle, and imbuing the abnormal tissue with its pe culiar colour. The colour of melanosis in the liver varies from a deep chocolate-brown to a rich black. Sometimes it is diffused in patches through the substance of the organ, at other times it exists in the form of rounded circum scribed tubercles of variable size and number. Lacnnec considers melanosis as an accidental tissue without analogue among the animal tis sues; he classes it with cancerous degenera tions, and describes it as existing in his two favourite conditions of crudity and softening. But the researches of Cruveilhier have shewn that in many instances melanosis is to be re ceived as a mere pigment, resembling the pig mentum nigrum of the choroid, which impresses its peculiar colour upon natural and morbid tissues, and he has also proved, in opposition to the view entertained by Laennec, that the softened state or state of infiltration very fre quently precedes the more dense and encysted form. Melanosis rarely exists in the liver with out being at the same time found in various other structures of the body, as in the brain, eye, lungs, heart, spleen, kidney, mucous mem brane, muscles, skin, &c.