HOMO. MAMMALIA. 37 



The vertebral column or spine is composed of thirty-two verte- 

 brae, seven of which are denominated cervical, twelve dorsal, five 

 lumbar, five sacral, and three coccygeal. Of the ribs seven pair 

 (called true ribs) are attached to the sternum or breast-bone by car- 

 tilaginous productions ; the other five pair are called false ribs. The 

 scapula has at the end of its projecting ridges a tuberosity called 

 the acromion, to which the clavicle is attached, and above its articu- 

 lation a point named the coracoid, for the attachment of certain mus- 

 cles. The radius turns completely on the ulna, in consequence 

 of the manner in which it is articulated with the humerus. The 

 carpus has eight bones, four in each row ; the tarsus seven ; those 

 of the rest of the hand and feet correspond with the number of toes 

 and fingers. 



The human race have rarely more than one child at each birth, 

 and twins do not occur in more than a single instance out of five 

 hundred. The period of gestation is nine months. The child at 

 birth is generally eighteen inches long, more than one-fourth of its 

 destined stature ; one-half is attained at two years and a half ; and 

 three-fourths at the age of nine or ten. The. growth generally 

 ceases about eighteen. The milk-teeth begin to shoot out a few 

 months after birth ; at two years old they are twenty in number, 

 and they fall successively towards the seventh year, to be replaced 

 by others. Of the twelve molar teeth which do not drop out, four 

 appear at about the age of four years and a half, four at nine years, 

 and the last four do not appear sometimes till the twentieth year. 

 Puberty is usually manifested by external signs, in girls at the age 

 of ten, twelve, or fourteen, and in boys from twelve to sixteen. The 

 male of the human species seldom exceeds six feet in height, and 

 is rarely under five feet ; the female is generally a few inches less. 



Scarcely has the body attained its destined height when it begins to 

 increase in bulk. Fat accumulates in the cellular tissue ; the diffe- 

 rent vessels are gradually obstructed ; the more solid parts grow 

 rigid; and after a life more or less long, more or less agitated 

 by physical or moral pleasure and pain, old age arrives, and in its 

 train decrepitude and death. While a few pass the limit of a hun- 

 dred years, the greater part of the race perish long before this 

 period by diseases or accidents, or even by old age itself. 



The greater part of animals are able at the moment of theiHkirth 

 to provide for their principal wants ; some of them, indeed, as Fish- 

 es, Reptiles, almost all Insects, and the Mollusca, never know their 

 parents. The Mammalia in general, and the Birds, remain for some 

 weeks in a state of great helplessness, but towards the eighth or tenth 

 day their senses are all developed, and some of them are even then 

 able to follow their mother. But Man, on the contrary, is at birth 

 the most helpless being imaginable ; even his senses, which require 

 a kind of education, are not developed till towards the fortieth day, 

 when the little being also begins to smile, and to know those who 

 approach him : 



" risu cognoscere matrem." 



