A very interesting address by the Hunterian Professor, Mr. Jonathan Hutchinson, was given in February, 1917, on Dupuytren’s work, especially in the discovery of the cause and treatment of the contraction of palmar fascia known by his name. Professor Hutchinson described his method of curing this by the removal of the head of the first phalanx, and showed excellent results and evidence of the formation of a perfect new joint to take the place of the old distorted one, and the fingers were as efficient as in the normal state in the exercise of flexion. He gives photographs of the hand some months after the operation showing it to be capable of easy and full extension as well as of flexion. This again agrees well with the cases of Sir W. MacEwen and Dr. Paterson of the formation of a functional joint by use and habit.
Another distinguished Hunterian Professor A. Keith, also gave two lectures in January, 1918, on the “Introduction of the Modern Practice of Bone-grafting,” which, in its modern form, he assigns to the credit of Sir William MacEwen. He lays great stress on the important work performed in such cases by the osteoblasts without whose living and formative action these results could not be obtained. He explains how necessary it is that these living elements should be stimulated into action by work. They thrive only so long as they have work to do. Another surgeon, Ollier, “wondered why the fragments of bone which he had succeeded in raising from slips of periosteum planted beneath the scalp or amongst muscles ceased to grow and tended to disappear. These bony grafts withered because they were not subjected to the strains and stresses which rouse the activity of osteoblasts.” MacEwen, “by a fortunate chance, planted his tibial grafts in a situation where they soon became subjected to muscular strains and stresses. In a short time bony fragments gathered from the legs of six boys became intrinsic parts of the humerus of a seventh; from the moment of primary union the bone cells of the graft were brought under the stimulating impulses of the biceps and triceps. Osteoblasts are the obedient slaves of muscles; muscular dominance is their breath of life.” (Italics not in the original.)
“Wolff was the first to devote thirty years of constant work and observation to prove that the shape and structure of growing bones and adult bones depend on the stresses and strains to which they are subjected. By altering the lines of stress the shape of a bone can be changed.”
Wolff’s law is simply this: “Osteoblasts at all times build and unbuild, according to the stresses to which they are subjected.”
Professor Keith says further: “We are driven, as I have pointed out in a previous lecture, to look for the primary cause, not in the bones, but in the muscles, particularly in those which are tonically and constantly in action so long as we are standing.”
A terse expression of Wolff’s law is quoted from Dr. John B. Murphy, of Chicago: “The amount of growth in a bone depends upon the need for it.”
A remarkable illustration of a similar process is given in the construction of sponges by the scleroblasts and it is stated: “The soft walls of this sponge are constantly exposed to the force of moving waters, and we shall see that the spicule-builders—the scleroblasts—are endowed with the same properties as osteoblasts—the powers of fashioning and depositing the elements of the skeleton so that the sponge can best resist the forces to which it is habitually exposed.”
One more important quotation from this lecture will suffice. “No one who has watched the behaviour of scleroblasts and marked the design in their workmanship can doubt that they have acquired certain characteristic qualities, chief of which is a sensitiveness to vibrations—to stresses. We see them build the same form of spicules as their ancestors, and therefore must suppose that their building quality is a gift of inheritance. We see them alter their mode of building as stresses change; we must therefore suppose that their inherited powers can be changed by the circumstances under which they work.”[69]
In regard to the action of the scleroblasts of sponges I have only to point out that the cautious words of Professor Keith on the treacherous ground of inheritance amount to the very same conception of personal selection and inheritance as are involved in the term “educability” of Sir E. Ray Lankester. Whether or not in the case of sponges this be a complete account of the matter it at any rate is a very important piece of evidence, if valid, for selection. Whether or not further it is a piece of evidence for a Mendelian factor implicit in the primordial sponges and released by some loss of inhibiting factors, as Professor Bateson would probably claim, is another and far more imaginative conception. The mere neo-Lamarckian with the aid of personal selection fails to see any difficulty in realising the wonderful process described by Professor Keith.
An apology must be offered here to the patient reader for the introduction under the heading of the “Evolution of a Bursa” of the apparently alien subjects of bone-grafts, artificial new joints and sponge-spicules, but I have hazarded the guess that all joints in all animals have been fashioned—“forged by the incident of use,” to employ a fine phrase of Professor Macdonald’s in another connection—in slow but intelligible ways by use, and that in them, as elsewhere, function has preceded structure. This arose so simply out of the story of the bursæ that I ventured to digress as aforesaid rather than make it the subject of a separate section.