56 THE BODY AT WORK 



of a leucocyte, or of an amoeba, is so deep a drop that we prefer 

 to recognize in the latter a merely chemical attractive force. 

 " Chemiotaxis " we term the influence which draws leucocytes 

 to the place where food is abundant ; although it is also the 

 place, one must admit, where in the interests of the body as 

 a whole they run great risk of asphyxiation. It is appetite 

 which draws a schoolboy to a bun-shop ; a sense of duty 

 prompts a fireman to risk his life in a chamber filled with 

 smoke. We have no desire to humanize a leucocyte ; but it 

 is difficult to emphasize too strongly its independence. It 

 would be absurd to use terms which imply that a leucocyte 

 has a self -directive power ; yet it is equally misleading to 

 describe its migration to the seat of injury, its retreat with 

 ingested germs to a lymphatic gland, its wriggling from the 

 lymph-ways of the gland into the shelter of its adenoid tissue, 

 in terms which imply that the forces which direct it are known, 

 and their mode of action understood. The success which 

 attends the inroads of germs is due to their amazing capacity 

 for multiplication when they reach lymph or blood. It is 

 useless to attempt to form an idea of the rapidity with which 

 they divide, since we have no data upon which to base cal- 

 culations. If the leucocytes fail to deal with the first few 

 that enter, germs soon swarm within the lymph- vessels. 

 This leads to an inflammation of the walls of the vessels, 

 which may then be seen as red lines beneath the skin. These 

 red lines lead upwards towards the nearest lymphatic gland. 

 The glands in the space behind the knee are not usually affected 

 when the focus of infection is in the foot. The red lines can 

 be traced up the inner side of the knee and the front and inner 

 side of the thigh to the groin. The glands in this situation 

 swell until they can be easily felt. If the mischief is in the 

 hand, the gland at the elbow may be affected, but most of 

 the lymphatics pass by it on their course to the glands in the 

 armpit. If a sore throat is the source of infection, the glands 

 beneath the angle of the jaw enlarge. Thus various glands 

 block the further progress of infection. In doing this their 

 resources may be strained to the uttermost ; they may enlarge, 

 become tender, grow soft, fill with pus, break down and dis- 

 charge the pus without the aid of a surgeon's knife, although 

 as soon as pus is recognizable within them it is wise to let it 



