298 OF THE PRIMARY TISSUES OF THE HUMAN BODY. 



5. Of the Simple Tubular Tissues ; Capillary Bloodvessels and 

 Absorbents. 



292. "We have seen that all the Animal Tissues, whose structure has been 

 yet considered, derive the materials of their growth and renovation from the 

 nutrient fluid; which is brought into a more or less close relation with their 

 elementary parts, by means of Capillary Bloodvessels. These seem to have a 

 claim to be regarded as among the elementary parts of the fabric; since they are 

 formed quite independently of the larger trunks, and have little in common with 

 them in their function. All those changes which take place between the blood 

 and the surrounding parts, whether ministering to the operations of Nutrition, 

 Secretion, or Respiration, occur during its movement through them; and the 

 function of the larger trunks is merely to bring to them a constant supply of 



Fig. 87. 



Capillary plexus in a portion of the web of & Frog's foot, magnified 110 diameters: 1, trunk of vein; 

 2, 2, 2, its branches; 3, 3, pigment-cells. 



fresh blood, regulated according to the demand created by the actions to which 

 it is subservient, and to remove the fluid which has circulated through them. 

 In Man, as in all the higher Animals in the adult condition at least the 

 Capillary circulation is entirely carried on through tubes having distinct mem- 

 months, was 4 feet and of an inch ; that of another boy, aged 8 years and 7 months, was 

 only 3 feet 1\ inches. According to the standard of height adopted by the Factory Com- 

 missioners (namely 3 feet 10 inches), the taller lad would have been judged fit for labor, 

 whilst the shorter would have been rejected. The Dentition of the latter, however, was 

 further advanced than that of the former; for he had two of the lateral Incisors, whilst 

 the former had only the central ; and the determination of their relative physical powers, 

 which would have been thus formed, would have been in complete accordance with the 

 truth. The elder boy, though shorter than the other by 5 J inches, possessed a much greater 

 degree both of corporeal and mental energy, and his pulse was strong and regular ; whilst 

 that of the younger lad, who was evidently growing too fast, was small and frequent. An 

 instance even more striking has come under the Author's own observation. 



