On the anatomy of a fin-whale (Physalus antiquorum, Gray) captured near Gravesend / by James Murie.

  • Murie, James.
Date:
[1865]
Catalogue details

Licence: Public Domain Mark

Credit: On the anatomy of a fin-whale (Physalus antiquorum, Gray) captured near Gravesend / by James Murie. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

    6/24 (page 210)
    the same manner as a boat is sculled by means of an oar over the stern When desirous of proceeding at a greater rate. the action of the tail is materially altered; instead of being moved laterally and obliquely, it strikes the water with the broad flat sur- face of the flukes in a direct manner upwards and downwards.” The first part of Beale’s description seems to me pretty well to explain the manner of action of the tail in gentle forward movement; for if we take it as a mere dynamical agent, then, according to the law of forces, the lobes of the tail, striking the water between the horizontal and vertical, would cause the body of the animal to move in the diagonal of these*. We have then to consider if the lobes do strike the water in this oblique manner. In illustration of its probability, I may mention that in this spe- cimen I noticed that as the lobes of the tail began to dry by the heat of the atmosphere they assumed opposite concavo-convex curves, so as to produce a very close resemblance both in curve and angle to the blades of a screw propeller. If this is what usually takes place in the movement of the tail, then one can readily understand that in the act of striking downwards and upwards with but a very slight lateral movement the water would receive an oblique stroke between the horizontal and vertical; in fact it would produce a more or less scooping, spiral, screw-like action, the consequence of which would be movement in the diagonal of the parallelogram of the resisting forces, from side to side, above downwards and below up- wards. As a further demonstration that something like this occurs, I may state that I observed in the mode of progression of the Porpoise lately exhibited in the Society’s Gardens a movement in the tail more or less resembling this. As the creature swam horizontally, and within a short distance of the surface, it struck the water up and down, but with an inclination of the lobes to the one or other side, adding to the obliqueness of the stroke by rolling its body slightly, so that the tail struck the water rather slantingly than directly up and down. When simply raising itself towards the surface (as, for instance, in breathing), or in descent, then the stroke seemed more flat, and the body, along with the tail, bent in a curve according as the movement was elevation or depression. In Physalus, the arch of the mouth, both antero-posteriorly and transversely, is much less than in the true Balcence; the length of the whalebone is also correspondingly shorter. In our specimen of P.antiquorum, the transverse curve of the former was about 72 inches at its widest, that is including the bony palate and the filaments of whalebone on either side; but towards the beak it became flattened and so narrowed that the chord of the arch was but 10 inches. The free palate itself in the middle of the mouth had a breadth of 1 2 inches. The outward exposed parts of the baleen in situ on one side mea- sured from the beak to the angle of the mouth in a direct line 126 * See article “ Motion,” ‘ Cyclop. Aunt, and Physiol.,’ vol. iii. p. 438. • [6]