764 THE POPULAR SCIENCE MONTHLY. 



and from those in the ancestral mammal which gave origin to the 

 giraffe. Each further stage of that growth which produced the large 

 fore-quarters and neck, entailed some adapted change in sundry of 

 the numerous parts composing the hind-quarters ; since any failure in 

 the adjustment of their respective strengths would entail some defect 

 in speed and consequent loss of life when chased. It needs but. to 

 remember how, when continuing to walk Avith a blistered foot, the 

 taking of steps in such a modified way as to diminish pressure on the 

 sore point, soon produces aching of muscles which are called into 

 unusual action, to see that over-straining of any one of the muscles of 

 the giraffe's hind-quarters might quickly incapacitate the animal when 

 putting out all its powers to escape ; and to be a few yards behind 

 others would cause death. Hence if we are debarred from assuming 

 that co-operative parts vary together even when adjacent and closely 

 united — if we are still more debarred from assuming that with in- 

 creased length of fore-legs or of neck, there will go an appropriate 

 change in any one muscle or bone in the hind-quarters ; how entirely 

 out of the question it is to assume that there will simultaneously take 

 place the appropriate changes in all those many components of the 

 hind-quarters which severally require re-adjustment. It is useless to 

 reply that an increment of length in the fore-legs or neck might be 

 retained and transmitted to posterity, waiting an appropriate varia- 

 tion in a particular bone or muscle in the hind-quarters, which, being 

 made, would allow of a further increment. For besides the fact that 

 until this secondary variation occurred the primary variation would 

 be a disadvantage often fatal ; and besides the fact that before such 

 an appropriate secondary variation might be expected in the course 

 of generations to occur, the primary variation would have died out ; 

 there is the fact that the appropriate variation of one bone or muscle 

 in the hind-quarters would be useless without appropriate variations 

 of all the rest — some in this way and some in that — a number of ap- 

 propriate variations which it is impossible to suppose. 



Nor is this all. Far more nuraerous appropriate variations would 

 be indirectly necessitated. The immense change in the ratio of fore- 

 quarters to hind-quarters would make requisite a corresponding change 

 of ratio in the appliances carrying on the nutrition of the two. The 

 entire vascular system, arterial and veinous, would have to undergo 

 successive unbuildings and rebuildings to make its channels every- 

 where adequate to the local requirements ; since any want of adjust- 

 ment in the blood-supply in this or that set of muscles, would entail 

 incapacity, failure of speed, and loss of life. Moreover, tlie nerves 

 supplying the various sets of muscles would liave to be proportionately 

 changed ; as well as the central nervous tracts from which they issued. 

 Can we suppose that all these appropriate changes, too, would be 

 step by step simultaneously made by fortunate spontaneous varia- 

 tions, occurring along with all the other fortunate spontaneous varia- 



