body, with composition chiefly of mannite or mannạ sugar, about 70 p. c., and residuum of common sugar and extractive. The greenish color of some specimens has been attributed to copper, but is really due to fraxin, a principle of the ash bark. Manna is soluble in 6.5 parts of water. It may be made artificially by treating glucose with sodium-amalgam. The export of Manna from Messina in 1877 amounted to about 57,000 kilgr.*

Use. The special action of this purgative has never been much investigated. In this country it is now less used than formerly; but it is considerably used in Italy and largely employed in South America. It has the peculiarity of being slow in action, but its action is apt to be maintained for some time when once it has been set up. Manna has superior value, or rather it has superior convenience as the laxative for the infant at breast or at the bottle; and has been too readily forgotten and superseded by certain other compounds which do not act so kindly either on stomach or bowels. By selection of the finer varieties of Manna, the infant's food can be sweetened as with sugar, or it will be accepted as a tasteful confection. Indeed, the coarser kinds are never desirable, being gritty and of resinous taste. An old-time association of senna and Manna has been mostly abandoned; when in use it was believed that senna thus combined was less drastic.

* F. & H. describe varieties of Manna produced by the birch, willow, eucalyptus, tamarisk, cotoneaster, and at least two forms of animal origin.

CHOLAGOGUES.

In the chapter on cathartic medication, the reason is given why it was not thought best to distribute purgative materials among the various sub-classes of laxatives, etc., etc., as is done by many writers upon this department of therapeutics. But in a treatise meant to be preeminently practical, there seems to be good ground for departure from this general scheme in the present instance; for there is no more frequent, no more important question presented to the mind of the physician, in the employment of purgatives, than that which concerns the selection of an agency which shall specifically affect the liver so as to promote the secretion of bile, as preliminary to its operation as a purgative. The term Cholagogue, Gr. zólos and ära, i. e., bile-driver, is unfortunate; but it has been sanctioned by too long usage to be set aside. That is strictly a bile-driver or expeller which evacuates the duodenum and the bowel below with such speed and force as shall carry before it all the bile which the intestine already contains, and thus prevents its reabsorption and return to the liver. But the term Cholagogue, as usually applied, has a very different signification; reference being had to whatever material may have the function of so impressing the liver as to secure the secretion, and conduct away from it, of new bile.

The literature of this branch of medicine has been

both enriched and obscured by many monographs written, many experiments performed and treatises based on experiments, all devoted to the general subject, during the last fifteen or twenty years. In 1866, a committee of the Medico-Chirurgical Society, appointed for such investigation, gave its majority report, after long and arduous labor, in effect that mercury is not cholagogue in its purgative action; this in the face of an almost universal opinion to the contrary, held by many generations of medical It is true that eminent members of the committee dissented from this conclusion, and that the minority report questioned its validity, suggesting, prominently, the following sources of error :—

men.

(1) The subjects of experiment were animals, mostly dogs, and it is conceivable that upon such subjects mercury may have a different action than upon man.

(2) The animals were in a state of health as concerns the liver; and it is not assumed that, in man, mercury promotes the flow of bile from a healthy liver.

(3) Many fibres of the sympathetic were mutilated or unavoidably sundered in the cutting operations incidental to insertion of the canula; and it is surmised, from analogy, that such mutilation might of itself modify the influence of so powerful an agent as mercury upon so important an organ as is the liver.*

*The clinical argument has not been introduced in the text. In the discussion which followed the presentation of this famous report, Dr. Gamgee remarked that, as one of the committee, of

The researches of many other investigators are well deserving of record, but it need only be added that, so lately as 1878, Professor Rutherford instituted careful enquiry into the actual influence over the bile-secreting function of many drugs which are commonly reputed to be cholagogue. His labors, in addition to affording many facts which will require to be quoted elsewhere, appear to justify the following general conclusions, viz.: (1) Contrary to expectation and previous opinion, it was quite conclusively proved that irritation or stimulation of the duodenal mucous membrane, although in the immediate neighborhood of the entrance of the common biliary duct, has no actual influence over the liver as respects secretion of bile.

(2) Repeated observations support the position that

which Dr. Bennett was chairman, he begged to express his opinion that the experiments had not conclusively proven that mercury does not act upon the liver. That mercury does influence those functions of this organ which have for an end and purpose the production of bile, is a clinical observation constantly repeated for ages; and it would be absurd to set up a few experiments made upon dogs against such constantly established experience. Professor Lister also bore testimony to the relief of especial symptoms of deranged biliary function, such as the cleansing of the skin and urine often effected by calomel, phenomena familiar to every physician, however they may be explained. Finally, in his inaugural address, as president, before the Association, in 1875, Sir Robert Christison used these words: "While deeply interested and much instructed by experiments performed by a committee of this Association, regarding the use of mercury, I remain as thoroughly convinced as ever, that this much-abused drug exerts a powerful action on a function of the liver, and is to be trusted as a most efficient remedy in the control of not a few of its disorders,"

those purgative agents which act most powerfully as glandular evacuants have the least power to evacuate bile from the liver, suggesting the formulation which has been previously employed, scil., that hydragogues are not cholagogues. This expression, however, may require slight modification as applied to actual practice; and in effect as follows: A diminished dose of a glandular cathartic, so operating as to cause a slight intestinal secretion, may also exert a slight influence over the liver. On the contrary, we are not warranted in believing that a drug which is mostly a peristaltic stimulant will therefore act upon the liver; and we know that senna, e. g., has little or no power over this organ.

Finally, the second general conclusion suggests an effective agency, in a direction in which the profession has but few and uncertain resources. There is no lack of materials calculated to promote the secretion of bile; it but needs to recognize them and to know how to apply them. There is no lack of materials capable of playing the rôle of literal bile-expellers; and by their free purgative evacuation they are readily brought to bear to drive the bile from the intestine which had previously been therein rendered. But how to depress bile-secretion or production, what remedies to apply to limit the liver in its fabrication, so to say, has been much more of a problem. It follows, however, from the researches. to which allusion has been made, that the hydragogue cathartic possesses somewhat of this inhibitory influence; probably by the effect it has to lower blood-pressure in the great organ within which the bile is secreted.