In Boston, Oliver Wendell Holmes (the father of the late Supreme Court 

 Justice Holmes) had suspected from his hospital experience that this septicemia, 

 or "rotting of blood", was due to something brought into the patient through 

 breaks in tissues. In Vienna and in other cities observant physicians and sur- 

 geons had come to the same conclusion. After Pasteur and Koch had made 

 their demonstrations, an English surgeon, working in Edinburgh, Joseph 

 Lister (1827-1912), hit upon the idea of keeping "germs" out of wounds. 

 He fitted his surgery up with suspended sheets that he soaked with carbolic 

 acid. He cleaned the wounds of his patients with this germ-killing solution. 

 And he promptly reduced the casualties following surgical operations. 



Since then many fl«//-septics have been used for destroying bacteria in 

 wounds of all kinds, and especially in surgery. The problem has always been 

 to find something powerful enough to kill all the kinds of germs, but not 

 likely to injure the host or the tissues. With the rapid development of syn- 

 thetic chemistry, the "sulfa" drugs have come in recent years to be widely 

 used with most amazing results (see page 242). They have been especially 

 valuable on the battlefield and in surgical situations complicated by fester- 

 ing. Many persons suffering from inflammation of the appendix come to the 

 surgeon after the appendix has burst. Then millions of bacteria of several 

 kinds are thrown into the body cavity, spreading the inflammation to the 

 tender tissues, frequently with fatal results. It has been found that pouring 

 dry sulfanilamide powder on the affected area soon destroys the germs and 

 gives the patient a chance to recover. Several hospitals have reported series 

 of from two to three hundred such cases without a death. 



The Chain of Infection^ It is not difficult to analyze the problem of 

 protecting a population against communicable diseases. In addition to what- 

 ever physicians and nurses can do for the patient attacked by a parasite, it is 

 necessary merely to attack the enemy at one of three points: (1) where para- 

 sites leave the host; (2) where parasites travel to another host; (3) where 

 parasites enter a new host. 



In actual practice, however, the task is not so simple. We need first to 

 know, in the case of each disease, something of the nature of the parasite or 

 virus. Then we have to know in exact detail just at what points and in what 

 manner it gets out of the patient, and just how it is carried from one host to 

 the next, and just how it enters the body. We cannot count upon complete 

 isolation either to render the present patient harmless or all possible victims 

 secure. 



The problem is complicated still further by the fact that several serious 

 diseases are transmitted by common insects. The common housefly, for exam- 

 ple, was found to be the chief vector, or conveyor, of typhoid-fever germs, and 

 later also of other intestinal parasites. A commission on the causes of epidemic 



*See Nos. 4 and 5, p. 639. 

 618 



