Description: Segment 1 After the credits, the narrator explains that we will be shown stages of the preparation and testing of diphtheria antitoxin, and that the laboratories and stables were filmed under wartime conditions. To combat diphtheria, sufferers and those they have come into contact with must be treated and also, all infants must be immunised. The narrator explains how diphtheria affects people, and an animation shows the spread of the toxin through the body. An animation also shows how a person carrying the infection can cause others to become infected. A guinea pig is used as an example of how easy it is to treat diphtheria 1/5000th of a millilitre of toxin is injected, as well as 1/100000th of a millilitre of antitoxin, and the guinea pig's life is saved. Next, the toxin is shown being prepared in a lab. A broth is made, then filtered, sterilised, incubated and then inocculated with bacillus, which is grown in the broth for ten days. The culture is seen after 24 hours and at the end of the ten days. Time start: 00:00:00:00 Time end: 00:05:30:22 Length: 00:05:30:22 Segment 2 The culture is transferred to a filter room where antiseptic is added to each bottle. Then the cultures are filtered and bulked. Preservative is then added and the liquid is pumped through sterilising candles. The toxin is then tested on guinea pigs. If at the correct toxicity, it should kill a guinea pig in five days. The toxin is then tested for potency. Next, the toxin is converted into a harmless preparation called Toxoid by adding Formalin. Toxoid is a valuable immunising agent, free of all active toxin. The narrator explains that the antitoxin is very closely associated with certain proteins of the serum of horses, which have been injected with Toxoid. Horses are kept at the laboratory stables for the preparation of antitoxin. The horses are shown arriving at the stables and being examined for suitability. They are also observed to ensure they are free from disease. The horses' blood is tested for any natural immunity. Finally, the horse is taken to the immunisation stables, where the course of immunisation begins. It is regularly dosed with diphtheria toxoid. Time start: 00:05:30:22 Time end: 00:11:20:17 Length: 00:05:49:24 Segment 3 The horse is observed and tested throughout the immunisation course. A graph shows the increase in amount of antitoxin produced by the horse during the course. The horse is shown being bled by the stable and laboratory staff 24 litres of blood is taken over eight days. After this, the horse is tested and when fit, another course is repeated. The antitoxin must then be extracted from the horse blood in as pure a form as possible. First the red blood cells are allowed to settle, next plasma is siphoned off, antiseptic added to the plasma, which is then bulked. The plasma is diluted with warm water, then hydrochloric acid, pepsin and ammonium sulphate are added. Time start: 00:11:20:17 Time end: 00:17:04:02 Length: 00:05:43:14 Segment 4 The preparation is then heated, making a precipitate of nonantitoxic solution, which is readily filtered off. Ammoniium sulphate is added and the antitoxin is precipitated. The antitoxin is filtered, leaving a cake of antitoxin, from which the ammoniium sulphate solution must be removed. The cakes are placed in cellophane bags, suspended in running water. After 48 hours, the bags contain antitoxin free from ammonium sulphate. An antibacterial agent is then added, and the solution then is concentrated by ultrafiltration. The concentrate is then passed through paper pulp and a filter candle. It is now ready but must be tested for sterility, non-toxicity and potency, and these testes are shown. Time start: 00:17:04:02 Time end: 00:23:12:03 Length: 00:06:08:00 Segment 6 The making of A.P.T. is shown. Next, charts show what happens during the course of immunisation. The level of antitoxin grows after the first injection, and is further stimulated by secondary injections. Three injections are usually needed to ensure that 90% of children are fully immunised. A child and a baby are shown being immunised. After the course, the Schick test is made to confirm that immunity has been achieved. A chart shows the death rates before and after active use of diphtheria immunisation programmes, and the narrator explains that during the war years there were more child deaths from diphtheria than from bombs. He concludes by saying that although much has still to be discovered, the battle against diphtheria is being fought successfully. Time start: 00:28:41:11 Time end: 00:34:06:20 Length: 00:05:25:08