Ii Modern Medicine

Boerhaave.

The i8th century dawned with the refreshing breeze of Newtonian philosophy blowing through it. During the previous 200 years there had been an immense amount of new and fruitful research along diverse lines. The new generation was bewildered with the mass and novelty of the material. Thus there is a period of pause and consolidation for the introduction of unitary conceptions into the mass of accumulated material. It was, moreover, a period of consolidation not only of ideas but also of teaching. These tasks at first turned men's minds away from the accumulation of further knowledge. The first half of the i8th century thus exhibits something of a gap in the prog ress of research. The medical field is largely filled by two great figures, Boerhaave and Haller.

Hermann Boerhaave (1668-1738) was the first great clinical or "bedside" teacher. (See BOERHAAVE.) Until the 17th century there was no systematic clinical teaching. The universities gave medical degrees on the basis of a spoken "disputation." No con tact with the patient was demanded. The first effective attempt to change this was at Leyden, where clinical teaching was insti tuted about 1636. Hermann Boerhaave was first appointed as a teacher at Leyden in 1701. At once the medical school attained a reputation which rapidly came to surpass even that of Padua. Boerhaave was a man of wide culture. To him, more than to any other man, we owe the modern method of medical instruction, especially in the English-speaking schools. Through his pupils he was the real founder of the Edinburgh Medical school, and through it of the best medical teaching in the English-speaking countries of the world.

Albrecht von Haller.

The only figure in the 18th century whose influence is comparable to that of Boerhaave is his pupil, the Swiss, Albrecht von Haller (1708-77) one of the most ac complished men of all time. (See HALLER, ALBRECHT VON.) Haller's great Elements of the Physiology of the Human Body (1759-66), marks the modernization of the subject of which it treats. He did work on the mechanics of respiration, on the formation of bone, on the development of the embryo, and on the action of the digestive juices. His most permanent contribu tions, however, are not so much contributions to knowledge as contributions to thought. Notable among these are his concep tions of the nature of living substance and of the action of the nervous system. These are still integral parts of physiological doctrine.

During the 17th century the favourite doctrine of nervous action supposed the existence of a nervous fluid. This, it was held, passed down the nerves to inflate or extend the muscle fibres. Inflation was supposed to shorten the fibres and so the muscle came to contract. An exquisite experiment made by Swammerdam, about 1665 with a nerve-muscle preparation, had, in fact, disproved this, but the experiment remained unpublished till 1736. So the matter stood till Haller's time.

Haller concentrated on an investigation of the muscle fibres. A muscle-fibre, he pointed out, had in itself a tendency to shorten with any stimulus, and afterwards to expand again to its normal length. This capacity for contraction, Haller, following a prede cessor, called irritability. He recognized the existence of "irri tability" as an element in the movement of the viscera, and notably of the heart and of the intestines. The feature of "irri tability" is that a very slight stimulus produces a movement al together out of proportion to itself, and continues to do this repeatedly so long as the fibre remains alive.

But besides the force inherent in a muscle-fibre, Haller showed that there was another force which comes to it from without, is carried from the central nervous system by the nerves and is the power by which muscles are normally called into action. This force, like that of irritability, is independent of the will, and like it can be called into action after the death of the animal. Haller thus distinguished the inherent muscular force from the extrinsic nerve force.

Haller next turned to consider sensation. He showed that the tissues are not, in themselves, capable of sensation, but that the nerves are the sole channels or instruments of this process. He showed how all the nerves are gathered together into the brain, and believed that they tended to its central part. Throughout his discussion Haller never falters in his display of the rational spirit. He develops no mystical or obscure themes, and although his view of the nature of soul may lack clarity, he separates such conceptions sharply from those which he is able to deduce from actual experience.

One of the ablest physiologists of the 18th century was an English country parson, the Rev. Stephen Hales (1677-1761). (See HALES, REV. STEPHEN.) By temper a biologist, he had received a training in mathematics and physics. With this ideal equipment, he proceeded to investigate the dynamics of the circu lation. His method consisted in applying the principle of the pressure gauge or manometer to living things. By tying tubes into the arteries and veins of animals, he measured blood-pres sure. He thus laid the foundation of an important mode of study ing disease. He computed the circulation rate and estimated the actual velocity of the blood in veins, arteries and capillary ves sels. He made a very important contribution by showing that the capillary vessels are liable to constriction and dilatation, a knowledge that has become of primary importance to the prac tising physician. He began to explore that wonderful mechanism of the heart by which the organ adjusts itself to its needs of out put. He exhibited his versatility by important contributions to many other departments as, for instance, his discoveries on respi ration, his improvements in ventilation, and his campaign for temperance.