Digestion in the Intestine. 179 



prolongation of the cecum, the vermiform appendix. This 

 appendix is frequently the seat of serious or fatal inflam- 

 mation, called appendicitis. This disease is not usually 

 caused by the lodging of seeds in the cecum, as most 

 people suppose ; still it is better not to swallow such things. 



A Simple Gland. A gland is a structure which takes 

 liquid from the blood and pours it out on some surface. 

 In its simplest form a gland is a mere pit, or hole, such as 

 the gastric glands, shown in Fig. 73. The blood capilla- 

 ries give off lymph around the gland, and from this lymph 

 the cells of the gland take their material. A sweat gland 

 needs more length than a gastric gland, and the extra 

 length is coiled up in a ball at the inner end. Many 

 small glands are forked at their inner ends, thus increas- 

 ing their surface. 



Kinds of Glands. Fig. 77 shows different forms of 

 glands, from the simplest to the most complex. In the 

 compound glands the lining of the duct, which is merely 

 a passageway, is different from the rest of the gland. 

 Glands that take waste matter from the blood are called 

 excretory glands, such as sweat glands ; they do not usu- 

 ally make much change in the material. Such glands as 

 the gastric glands change the material that they pour out; 

 the gastric juice is different from anything found in the 

 blood. Such glands are called secretory glands. Sweat is 

 an excretion ; gastric juice is a secretion. Still, all glands 

 are said to secrete, that is, to separate something from the 

 blood. And gland action in general is called secretion. 

 In structure, then, glands may be simple or compound. 

 In function they may be excretory or secretory. 



Control of Glands. All glands are under the control 

 of nerves. But this control is involuntary, and under the 



