The liver is more liable to the formation of encysted tumors than any other parenchymatous organ; and we repeat that the rarity of tubercular deposit in the liver enhances the importance of the hydatid theory. We find in the liver aa. The simple serous cyst, a serous sac containing a clear watery fluid; this is not met with as often as;

PP. The acephalocyst of Laennec; which in the first instance is merely a serous, but from acquiring a fibrous investment, is converted into a fibro-serous sac, containing, besides serum, the so-called acephalocysts; these are small bladders (hydatids), formed of coagulated albumen and filled with an albuminous fluid; they vary in size and number, and are either attached to the parietes of the former or float in the serum.

The acephalocyst generally attains a considerable size in the liver. We have several extraordinary specimens in the Viennese museum, and there is one of a foot in diameter. In proportion as the heterologous growth increases, the hepatic parenchyma gives way, and the nearer the former originally was to the surface, the sooner will it reach the peritoneal investment; it then projects above the liver, with a larger or smaller segment of its circumference. Under these circumstances the peritoneum invariably inflames, and the consequence is a thickening of the latter upon and in the vicinity of the acephalocyst; an investment of pseudomembranous cellular tissue is formed, by which the viscus becomes attached and agglutinated to adjoining organs.

Sometimes there is but one, sometimes there are several of these cysts; in rare cases, the entire liver appears converted into an aggregation of larger or smaller sacs. In the latter instance, two or more are often found to communicate with one another; either in consequence of atrophy of their parietes from pressure, of rupture from inflammation, or from a sudden increase in their contents.

The right lobe of the liver is the ordinary seat of the acephalocysts; the largest are always found at this part.

Acephalocysts are liable to inflammatory attacks, which entirely resemble those of normal serous and fibro-serous membranes, both in regard to the exudations they give rise to, as to their terminations and consecutive results. They may, by causing suppuration and obliteration, de-troy the vitality of the acephalocysts, and thus bring about a cure.

The hepatic acephalocyst may discharge its contents in various directions; the portion that projects above the surface of the organ, and has lost the support it previously received from the surrounding parenchyma, may become atrophied and thinned, or its tissue be weakened or destroyed by inflammation and suppuration, and thus communicate directly with the abdominal cavity; or having first become agglutinated to neighboring viscera, it may perforate the latter and discharge externally, or into other cavities and canals. The contents may thus make their way:

Into the right pleura, or into a pulmonary abscess, and be removed by the bronchi:

Into the intestinal cavity, and especially into the duodenum and transverse colon, so as to pass off by vomiting or defecation:

Into the gall-ducts, i. e. into a large branch of the ductus hepaticus, by which passage they may ultimately be conveyed into the intestine; though the protrusion of the acephalocyst more frequently induces dangerous obstruction of the biliary passages:

In rare cases, into a neighboring bloodvessel, and lastly:

Into a neighboring circumscribed abscess, resulting from peritoneal inflammation.

Occasionally the acephalocyst opens in various directions at once. After the discharge of its contents, obliteration of the sac and cure, sometimes follow.

The contents of the sac are discharged unaltered or changed, according to the process accompanying its perforation; the products of inflammation in the matrix, or of the parietes of other cavities (e. g. the pleura), the bile, the intestinal secretions, etc, are particularly prone to induce a maceration and complete solution of the acephalocyst.

On the other hand, not only the parietes of the investing sac are often found saturated with bile, but the bile extravasated from large gall-ducts is frequently mixed with its contents, and its parietes are incrusted with inspissated bile. In the same manner we may now and then discover blood in the cyst, which has been discharged from neighboring vessels.

The hepatic parenchyma is forced out of its position in proportion to the size and number of the cysts; if otherwise affected, it presents the nutmeg degeneration.

Acephalocysts in the liver are frequently complicated with affections of the same kind in other organs, as the lungs, spleen, and kidneys; the disease is also complicated with cancerous affections in other organs. Large acephalocysts of the liver give rise to ascites or peritonitis, and may thus prove fatal.

In reference to the etiology of these growths, it appears, according to some observations, that mechanical injury of the liver and intermittent fevers may influence their development. They seem not to occur before puberty.