IN THE LIMBS OF MAMMALIA. 19 



The heart, notwithstanding its lofty physiological preeminence, is, morphologically, 

 only a more or less complicated enlargement and convolution of the great arterial trunk, 

 just as the brain and stomach are teleological modifications of more simple fundamental 

 parts ; it and the stomach are examples of lateral displacement from their normal position 

 as median organs. Terminating the vagina is the uterus, of which the longitype is not 

 yet discovered ; the mouth is the longitype of the vaginal opening into the alimentary 

 canal, of which latter, however, it is the teleological inlet. Pathology seems to indicate 

 that the testes and the parotid glands are longitudinally homologous ; for inflammation 

 of the former is very prone to invade the latter, by what is called metastasis, but which in 

 this case may be a physiological indication of a morphological relation otherwise obscure. 

 So, likewise, are connected the diseases and their remedies, of the genito-urinary and 

 respiratory passages, and both these cases, with that of the irritation of the nostrils sym- 

 pathetic with the presence of worms in the rectum, are simply analogous to what so often 

 happens between parts which are laterally homologous. I am not aware that any dispo- 

 sition has yet been proposed of the other abdominal viscera, liver, spleen, pancreas, and 

 kidneys ; and will merely refer to the view of J. Maclise concerning the two former, that 

 they are laterally complementary, as stated on page 153 of his "Surgical Anatomy," where 

 are also given several reasons for his opinion. 



We come now to the limbs, of which there are, in vertebrates, two pairs: the one anterior, 

 and the other posterior. Their general homology as diverging appendages of the haemal 

 arches of the occipital or posterior cranial, and of the anterior pelvic vertebrae, has been 

 already indicated ; and also the doubt as to the general and antitypical relations of the 

 lower or heemapophysial portions of those arches, supposed to be represented by the four 

 bones, clavicle and coracoid, ischium and pubis. In many mammalia the two former exist 

 only in the shape of processes from the scapula, which is the upper or pleurapophysial por- 

 tion of the arch; this and its antitype the ilium, seem to follow the direction of the devel- 

 opment of the vertebral column, the former pointing forward, and the latter backward. To 

 the lower or distal ends of these elements, by the shoulder and hip joints, are articulated the 

 proximal ends of the limbs proper ; these are made up each of four segments ; anteriorly, 

 of the arm, fore-arm, hand, (wrist and palm,) and fingers ; or, osteologically, of the humerus, 

 ulna and radius, carpus and metacarpus, and phalanges ; and posteriorly, of the thigh, leg 

 foot, (ankle and instep,) and toes ; or, of the femur, tibia and fibula, tarsus and metatarsus, 

 and phalanges. 



It is worthy of remark, that the number of component parts of the segments increases 

 toward the distal ends, while their individual mobility is diminished in the same direction 

 as if for mutual compensation, and in accordance with the general rule that the right of dis- 

 cretion increases and diminishes with responsibility. 



Now the law of polarity is morphological ; but in this case, the teleology also is very evi- 

 dent ; the divergence of the scapula and ilium is on the principle of a pyramid, the base 

 being wider than the top, so as to afford a firmer support; we shall find the same polarity 

 carried out in the segments of the limbs themselves with one exception, the necessity of 

 which is, however, as obvious as the grounds for the general arrangement therein departed 

 from; and indeed throughout the limbs, which as "a whole are teleological superadditions, 

 the uses of the general laws are so apparent that the latter seem almost teleological, the 

 two principles being, as it were, blended and thoroughly harmonious. 



The general correspondence between the four segments of the anterior and posterior 



