70 CHAPTERS ON EVOLUTION. 



which everywhere and primarily distinguish it as living matter. It 

 remains to be seen whether the examination of higher animal life 

 will destroy the analogies and similarities which are so plainly 

 apparent in the lower confines of the kingdom of living nature. 



In its complex entirety, the body of a man appears to present us 

 with no features of structural kind which can serve in the least 

 degree to approximate the higher type to lower forms and types of 

 life. Organ and parts in systems and series more or less compli- 

 cated, constitute the framework of the body, whose physiology or 

 functional activity is in turn of a correspondingly intricate character. 

 The simplest tissue of man's frame would, at first sight, appear to- 

 present a complexity defying reconciliation with any simpler phase of 

 structure or life. What seems true of the human type may be held to 

 be equally correct when applied to the case of much lower animals, 

 which appear to be far enough removed in their own way from the 

 primitive simplicity of the protoplasmic Amoeba and its allies. A 

 snail or a worm, at first sight, appears, in fact, to be as distant from 

 the protoplasmic and primitive stage of organisation as man him- 

 self, in that each is built up of organs exhibiting a complicated 

 structure and highly specialised arrangement of parts. In such a 

 case, what are the likenesses or differences between the higher and 

 lower organisms which the scientific examination of the complex 

 frame reveals? Let anatomy and physiology together furnish the reply. 



The microscopic anatomy of the tissues of which man's body con- 

 sists, reveals to us a fundamental unity of organisation, which is both 

 striking and important in all its particulars and aspects. Every 

 primer of physiology teaches us the lesson that man's body, like the 



FIG. 22. VARIOUS CELLS : a, diagram of a cell ; I, fat cells ; c, d, nerve-cells ; 

 e, cartilage-cells ; f, pigment-cell ; g, a plant-cell ; h, liver-cells ; i, cartilage-cell. 



frames of all other animals above the rank of the Amoeba and its nearest 

 kith and kin, consists of definite layers of minute " cells " (Fig. 22), 

 grouped together to form the definite " tissues " of the body. When 



