474 



KNOWLEDGE & SCIENTIFIC NEWS. 



[July, 1906. 



The second illustration to this article shows the ex- 

 ternal vestiges of the hind-limbs in an African python 

 {python sebce) over twenty feet in length. These 

 vestiges take the form of a pair of horny spurs, or 

 claws, about three-quarters of an inch in length, and 

 situated on the under surface of the body at the com- 

 mencement of the tail. In the specimen figured, the skin 

 has been slit along the middle lire of the belly, so that 

 the two claws are separated from one another by the 

 width of the skin of the back and flanks, whereas in 

 nature they would be comparatively close together. 

 Each claw in this specimen was supported on a bony 

 core, corresponding to the terminal bone of one of the 

 toes of a lizard's foot, while eml>edded in the flesh 

 beneath was a much stouter bone, probably represent- 

 ing the femur, or thigh-bone, and also a minute nodule, 

 which may be the last remnant of the pelvis. It must 

 not, however, be suppo.sed that all pythons exhibit 

 these vestiges as distinctly as in this specimen. On 

 the contrary, in the skin of a Malay python [P. molurus) 

 of five-and-twenty feet in length, which I recently ex- 



Fig. 2.— Part of the Skin of the Tail of a Python, showing the 

 Horny Spurs representing the Hind Limbs. 



amined, the external rudiments of the limbs were 

 minute lobes, scarcely larger than the head of a big 

 pin. Somewhat similar vestiges of the hind-limbs are 

 retained in the small burrowing tropical snakes of the 

 family Typhlopidce, as well as in the members of a 

 nearly allied group; but in no snakes have any traces cf 

 the front-limbs been detected. 



Tliese vestiges, then, afford decisive evidence that 

 snakes are descended from reptiles with functional 

 hind-li.iibs, from which it may also be inferred that their 

 early ancestors were four-limbed; the front limbs, as 

 in the case of certain snake-like lizards, being the first 

 to disappear. The further inference that those snakes 

 which retain rudimentary hind-limbs are the most 

 archaic members of their kind, has been recently con- 

 firmed by the discovery that pythons and boa-constric- 

 tors display certain primitive features in other parts of 

 their anatomy. 



Space admits of but very brief allusion to the case 

 (if whales. .As everyone knows, all the members of 

 the order Cetacea, inclusive of whales, dolphins, por- 

 poises, &c., have but a single pair of limbs, the front 

 pnes, which are modified into paddles for swimming. 



It is, however, far less well known that deep down 

 among the muscles of the body of the Greenland right- 

 whale and its immediate relatives are embedded cer- 

 tain small and useless bones which represent those of 

 the pelvis, and part of the hind-limbs of less specialised 

 mammals. These rudimentary bones are alone sufficient 

 to demonstrate the descent of whales and dolphins from 

 four-limbed ancestors; and when taken in connection 

 with the fact that cetaceans are air-breathing (as op- 

 posed to gill-breathing) creatures, lead to the conclu- 

 sion that their ultimate ancestors were terrestrial. 

 Curiously enough, it is the most specialised whales 

 (that is to say, the true, or whale-bone whales) that 

 alone retain rudiments of the hind-limb itself; these 

 vestiges in the toothed whales, such as the sperm- 

 whale and dolphins, being restricted to the bones of the 

 pelvis. In this respect, then, cetaceans are unlike 

 snakes, in which, as we have seen, it is the most primi- 

 tive forms that alone retain vestiges of limbs. 



Turning to the subject of the third illustration, we 

 have an exceedingly interesting example of a more or 

 less completely rudimentary structure, in the so-called 

 worm-like appendage, or appendix vermiformis, of the 

 human blind gut, or ccecum. In this connection it may 

 be well to mention incidentally that the disease to 

 which this organ is so frequently subject, derives its 

 name of appendicitis from the organ itself, and its al- 



Fig. 3. The Vermiforn 



ternative title of typhlitis, from the Greek 7-i'0X:s, blind, 

 in reference to the blind gut of which the appendix 

 forms the termination. 



In a great number of mammals, both herbivorous and 

 carnivorous, there exists at the angle formed by the 

 junction of the small intestine or ileum with the large 

 intestine or colon, a large blind pouch or diverticulum, 

 which probably aids in the digestion of food bv pre- 

 venting its toO' rapid discharge. The ca»cum, as it is 

 called, is remarkably w^ell developed in the horse and 

 the dog, in the latter of which it is coiled in a spiral 

 manner. In the human subject, on the other hand, the 

 Cfficum proper is very short, but is prolonged by the 

 aforesaid vermiform appendage, which is usually from 

 four to five inches in length, with a calibre of cnly 

 about one-third of an inch. This appendage corre- 

 sponds to the coiled caecum of the dog, of which it is 

 obviously an aborted rudiment. .As many of us know 

 by sad experience, it is only too likely to become choked 

 by closely packed, partially digested, or undigested 

 food; and the opinion has been very generally held 

 that it is an altogether superfluous and u.seless organ 

 whose complete elimination would be an immixed ad- 

 vantage to the human race. For instance, on page 

 282, of " The -Student's Darwin," by Dr. .\veling, we 

 find the following statement in reference to the ver- 

 miform appendage : — 



