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CONCLUDING REMARKS. 



THE Shoulder-girdle has now been traced from the Skate, and the Sternum from the 

 Salamander, both up to our own species. 



Along this devious journey the attention of the reader has not been diverted by reference to 

 any ideal " Exemplar," nor even by any remarks upon the teleological meaning of the parts 

 described. Structural fitnesses are self-evident in most cases, and no one could be found to 

 follow the details of a bald and positive Memoir like the present, whose own mind would not in 

 each case intuitively supply this apparent deficiency. Not only is a teleological explanation a mere 

 impertinence in a morphological work, it is also a Massing hindrance a pretty golden ball that 

 diverts the racer from his course. It may be remarked, also, that morphological science is more 

 perfectible than teleological, the latter being often very difficult, and even, in some cases, of 

 impossible attainment, but morphology only requires materials and patience to enable us to 

 acquire a very clear conception of the step-by-step stages of anatomical structure. I trust that 

 I have fairly unravelled the Shoulder-girdle from the Sternum ; this was a piece of work which 

 kept everything else waiting, and I have not found anything satisfactory on this head in the 

 best recent works upon the subject. The distinction between the ectosteal sheath of a carti- 

 laginous rod or plate and a tract of ossified membrane (aponeurotic bone, parostosis) is one of 

 vital importance, and has been extremely difficult to demonstrate with absolute certainty ; this, 

 in the most difficult instances, is explained by the process of osseous grafting, such as often 

 takes place in the Warm-blooded Classes. I have endeavoured to give a real morphological 

 importance to many fenestrse, notches, and interspaces, that have hitherto seemed to be 

 meaningless, but which, being rightly interpreted, throw a very clear light upon the structures 

 which they in a greater or less degree subdivide. 



On the whole, the ascent in the morphology of the regions here treated of is very regular, 

 the greatest and most sudden changes in the parts appearing in the Birds and Mammals, 

 an amount of metamorphosis taking place in them far beyond anything I expected to find. 



These metamorphic modifications, whilst they have imparted a great charm to this piece of 

 research, have also required no little labour and patience. 



The first instance I have given of the Shoulder-girdle (in the Skate) may be compared to a 

 clay model in its first stage, or to the heavy oaken furniture of our forefathers, that " stood 

 ponderous and fixed by its own massy weight." 



As we ascend the vertebrate scale, the mass becomes more elegant, more subdivided, and 

 more metamorphosed, until in the Bird Class, and amongst the Mammals, these parts form the 

 framework of limbs than which nothing can be imagined more agile or more apt. So, also, as 

 it regards the Sternum, at first a mere outcropping of the feebly developed costal arches in 

 the Amphibia, it becomes the keystone of perfect arches in the true Reptile ; then the fulcrum 

 of the exquisitely constructed organs of flight in the Bird ; and lastly, forms the mobile front-wall 

 of the heaving chest of the highest Vertebrate. 



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