medical essays-第52章
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art takes what it wants by the divine right of the omnipotent nucleated cell。 The organism has become； in the words already borrowed from Virchow； 〃a sum of vital unities。〃 The strictum and laxum； the increased and diminished action of the vessels； out of which medical theories and methods of treatment have grown up； have yielded to the doctrine of local cell…communities； belonging to this or that vascular district； from which they help themselves； as contractors are wont to do from the national treasury。
I cannot promise to do more than to select a few of the points of contact between our ignorance and our knowledge which present particular interest in the existing state of our physiological acquisitions。 Some of them involve the microscopic discoveries of which I have been speaking； some belong to the domain of chemistry； and some have relations with other departments of physical science。
If we should begin with the digestive function； we should find that the long…agitated question of the nature of the acid of the gastric juice is becoming settled in favor of the lactic。 But the whole solvent agency of the digestive fluid enters into the category of that exceptional mode of action already familiar to us in chemistry as catalysis。 It is therefore doubly difficult of explanation； first； as being； like all reactions； a fact not to be accounted for except by the imaginative appeal to 〃affinity；〃 and secondly； as being one of those peculiar reactions provoked by an element which stands outside and looks on without compromising itself。
The doctrine of Mulder； so widely diffused in popular and scientific belief； of the existence of a common base of all albuminous substances； the so…called protein； has not stood the test of rigorous analysis。 The division of food into azotized and non…azotized is no doubt important； but the attempt to show that the first only is plastic or nutritive； while the second is simply calorifacient； or heat…producing； fails entirely in the face of the facts revealed by the study of man in different climates； and of numerous experiments in the feeding of animals。 I must return to this subject in connection with the respiratory function。
The sugar…making faculty of the liver is another 〃catalytic〃 mystery； as great as the rest of them； and no greater。 Liver…tissue brings sugar out of the blood； or out of its own substance；why？
Quia est in eo Virtus saccharitiva。
Just what becomes of the sugar beyond the fact of its disappearance before it can get into the general circulation and sweeten our tempers； it is hard to say。
The pancreatic fluid makes an emulsion of the fat contained in our food； but just how the fatty particles get into the villi we must leave Brucke and Kolliker to settle if they can。
No one has shown satisfactorily the process by which the blood… corpuscles are formed out of the lymph…corpuscles； nor what becomes of them。 These two questions are like those famous household puzzles；Where do the flies come from？ and； Where do the pins go to？
There is a series of organs in the body which has long puzzled physiologists；organs of glandular aspect； but having no ducts；the spleen； the thyroid and thymus bodies； and the suprarenal capsules。 We call them vascular glands； and we believe that they elaborate colored and uncolored blood…cells； but just what changes they effect； and just how they effect them； it has proved a very difficult matter to determine。 So of the noted glandules which form Peyer's patches； their precise office； though seemingly like those of the lymphatic glands； cannot be positively assigned； so far as I know； at the present time。 It is of obvious interest to learn it with reference to the pathology of typhoid fever。 It will be remarked that the coincidence of their changes in this disease with enlargement of the spleen suggests the idea of a similarity of function in these two organs。
The theories of the production of animal heat； from the times of Black； Lavoisier； and Crawford to those of Liebig； are familiar to all who have paid any attention to physiological studies。 The simplicity of Liebig's views； and the popular form in which they have been presented； have given them wide currency； and incorporated them in the common belief and language of our text…books。 Direct oxidation or combustion of the carbon and hydrogen contained in the food； or in the tissues themselves； the division of alimentary substances into respiratory； or non…azotized； and azotized；these doctrines are familiar even to the classes in our high…schools。 But this simple statement is boldly questioned。 Nothing proves that oxygen combines （in the system） with hydrogen and carbon in particular； rather than with sulphur and azote。 Such is the well… grounded statement of Robin and Verdeil。 〃It is very probable that animal heat is entirely produced by the chemical actions which take place in the organism； but the phenomenon is too complex to admit of our calculating it according to the quality of oxygen consumed。〃 These last are the words of Regnault； as cited by Mr。 Lewes； whose intelligent discussion of this and many of the most interesting physiological problems I strongly recommend to your attention。
This single illustration covers a wider ground than the special function to which it belongs。 We are learning that the chemistry of the body must be studied； not simply by its ingesta and egesta； but that there is a long intermediate series of changes which must be investigated in their own light； under their own special conditions。 The expression 〃sum of vital unities〃 applies to the chemical actions； as well as to other actions localized in special parts； and when the distinguished chemists whom I have just cited entitle their work a treatise on the immediate principles of the body； they only indicate the nature of that profound and subtile analysis which must take the place of all hasty generalizations founded on a comparison of the food with residual products。
I will only call your attention to the fact； that the exceptional phenomenon of the laboratory is the prevailing law of the organism。 Nutrition itself is but one great catalytic process。 As the blood travels its rounds； each part selects its appropriate element and transforms it to its own likeness。 Whether the appropriating agent be cell or nucleus； or a structureless solid like the intercellular substance of cartilage； the fact of its presence determines the separation of its proper constituents from the circulating fluid； so that even when we are wounded bone is replaced by bone； skin by skin； and nerve by nerve。
It is hardly without a smile that we resuscitate the old question of the vis insita of the muscular fibre； so famous in the discussions of Haller and his contemporaries。 Speaking generally； I think we may say that Haller's doctrine is the one now commonly received； namely； that the muscles contract in virtue of their own inherent endowments。 It is true that Kolliker says no perfectly decisive fact has been brought forward to prove that the striated muscles contract with。 out having been acted on by nerves。 Yet Mr。 Bowman's observations on the contraction of isolated fibres appear decisive enough （unless we consider them invalidated by Dr。 Lionel Beale's recent researches； tending to show that each elementary fibre is supplied with nerves； and as to the smooth muscular fibres； we have Virchow's statement respecting the contractility of those of the umbilical cord； where there is not a trace of any nerves。
In the investigation of the nervous system； anatomy and physiology have gone hand in hand。 It is very singular that so important； and seemingly simple； a fact as the connection of the nerve…tubes； at their origin or in their course； with the nerve…cells； should have so long remained open to doubt； as you may see that it did by referring to the very complete work of Sharpey and Quain （edition of 1849）； the histological portion of which is cordially approved by Kolliker himself。
Several most interesting points of the minute anatomy of the nervous centres have been laboriously and skilfully worked out by a recent graduate of this Medical School； in a monograph worthy to
