typhoid germs are placed in the peritoneal cavity of a rabbit thus immunized and examined from time to time under a microscope, they are seen to dissolve in the peritoneal fluid much the same as sugar dissolves in tea. In other words, this rabbit has protected itself against the invasion of typhoid germs by producing a substance or power in its fluids which dissolves and disintegrates the germs themselves. Another example of lytic immuity, probably, is the socalled anaphylaxis of which we hear so much today. If a guinea pig be injected subcutaneously with a small dose of horse serum, no effect is observed more than would have been produced by the injection of so much distilled water. However, if two weeks later this same guinea pig be injected with a second dose of horse serum, the guinea pig will die very promptly, sometimes within ten to twenty minutes, and with a definite train of symptoms. Furthermore, if horse serum be dried and ground and digested with alkaline alcohol, it can be split up into two parts, one of which is poisonous to guinea pigs and the other nonpoisonous. Now if this poisonous portion be injected into a guinea pig, the guinea pig will die with the same train of symptoms that the guinea pig manifested which was injected with the second dose of horse serum. All of which probably means that the guinea pig, upon receiving the first dose of horse serum, at once proceeded to eliminate, to get rid of, this foreign proteid material that had been thrown into his system. The guinea pig had no experience to go on; such a thing had never happened before; neither he or his ancestors had ever experienced such an attack; the cells and tissues at once went to work to dispose of and eliminate this foreign material. Apparently he succeeded in doing so by the production of a ferment which broke up the serum into portions similar to the poisonous and nonpoisonous portions produced by the digestion of horse serum in alcohol, but the process being new to the guinea pig, went on so slowly that the poisonous portion did no harm. Now, exactly the same as in the production of antitoxin, the cells having learned to do this, retain their power, remember how it was done, accumulate a store of the necessary chemical substance and remain particularly sensitive to such invasion. Consequently when the second amount of horse serum is injected into the guinea pig, the ferment present promptly splits up the horse serum into a poisonous and nonpoisonous portion, and the poisonous portion being large in amount kills the animal. The guinea pig in its anxiety to get rid of this foreign material, overstepped itself and produced its own death. In the condition following the first injection.

of horse serum, when a second dose would kill him, the guinea pig is spoken of as "sensitized" toward horse serum.

There is another feature of this work which corroborates this view. If a guinea pig be injected in the usual way with a small dose of horse serum, and two weeks afterwards if he be injected with an amount of horse serum less than the amount necessary to produce his death, he may show some symptoms following the injection, but rapidly recovers and afterward is apparently a normal guinea pig. In other words, the injection of this dose less than the fatal dose had "desensitized" the guinea pig, which can be explained by supposing that the guinea pig in breaking up and disposing of this second smaller dose of serum has used up his available supply of ferment, consequently when injected the next day with a fatal dose of serum he has no ferment on hand with which to break it up, and hence it does not kill him. If, however, the guinea pig be allowed time following this second nonfatal injection to accumulate a second. supply of ferment then the injection of a fatal dose of serum will kill him as promptly as before.

Another illustration of lytic immunity is found in the so-called tuberculin reaction. It is a well-known fact that if tuberculin be injected into a normal person or a normal animal, no particular symptoms are produced, but that the injection of tuberculin into a tuberculous animal will produce what is known as the tuberculin reaction, rise of temperature, loss of appetite, swelling at the point of injection and general feeling of depression. This means that the normal person or normal animal, never having had experience with tuberculin or with tubercle products, when injected with tuberculin, must devise its own means of disposing of this new foreign substance, must learn how to destroy it which takes time, and the substance is destroyed slowly and produces no symptoms. However, the tuberculous person or animal, having had experience with tubercle products absorbed from its own lesion, is prepared with its ferment or with its other means of defense, and when tubercle products (Tuberculin) are injected, very promptly breaks them up into a poisonous and nonpoisonous portion, and thus produces what is known as the tuberculin reaction. A larger dose of tuberculin may very easily kill the tuberculous animal. Not only does the system as a whole become thus "sensitized" to tubercle products, but every tissue in the body apparently gains the power. For example, if a portion of the skin be lightly scarified and if a drop of tuberculin be rubbed into this scarified area there results a distinct reaction, the skin becoming red, inflamed, and papules or vesicles may form, which do not subside for

a number of days. This is usually called Von Pirquet's skin reaction. Again, if a drop of purified tuberculin be instilled into the eye, the eye becomes red and inflamed, showing that the tissues of the eye have the power to break up tubercle products into an irritant and nonirritant portion, and the irritant portion causes the reaction. This is the well-known eye test, the Calmette ophthalmo-reaction for tuberculosis.

Another form of immunity is the so-called phagocytic immunity, in which the body defends itself against invading bacteria by means of the leucocytes, or white blood cells. The leucocytes are selfsustaining, independent cells which inhabit our blood stream and our tissues. They lead a roving life, and their purpose is to defend the body against invading bacteria and to assist in the repair of any damages which may occur to the tissues. They protect the body against invading bacteria by taking the bacteria up into their own substance and digesting them, thus causing their complete disappearance.

So far we have looked upon only one side of this battle which is carried on between man and invading diseases, namely the defense a man puts up against the germs. But we must not forget that the invading bacteria are living matter just as truly as the cells of our body, and as such they manifest the intelligence inherent in living matter. In other words, the bacteria become immunized to us as well as we to the bacteria. In this case the bacteria put up a means of defense against the attack of our phagocytes so complete in many cases that the leucocytes are utterly unable to take up the bacteria. When this occurs our system puts up another means of offense against the bacteria. There is produced in our blood serum a substance, which, by acting on the bacteria, neutralizes in some way their defense against the leukocytes, so that the bacteria which have been first attacked by our blood serum can then be taken up by the phagocytes, and this power which exists in the blood serum is called. opsonic power. Now the efficiency with which the leukocytes in a man's blood can protect him against any particular strain of bacteria depends upon the efficiency of his blood serum to prepare the bacteria for phagocytosis. By a simple laboratory technique we can measure the comparative efficiency of my blood serum to opsonize bacteria with any other blood serum which may come into my hands, and in this way the power of a person to resist the attack of a certain disease can be measured. When the opsonic power is high, the patient has good defensive power against that particular microorganism. When the opsonic power is low, the bacteria tend to predominate.

Now the patient's power of defense against any invading microorganism can be trained and developed. If a patient come into the office with the opsonic index low toward staphylococcus and he gives a history of having suffered from repeated attacks of boils one can help that patient by training him to defend himself against the invasion of staphylococci; and this training can be done only according to the old methods of nature, that is, learning to do by doing. If his tissues are unable to defend themselves against staphylococci, they must be given staphylococci to practice on. Being unable to defend themselves against living staphylococci, they are given. dead staphylococci, and the dead staphylococci are administered in the form known as bacterial vaccines. The germs are emulsified in physiological salt solution, are killed by heat and the strength of the mixture determined. When these dead germs are injected into the patient, the tissues of the patient, by breaking up and eliminating these dead germs, learn how to dispose of the living germs, and the patient gradually acquires immunity, or the power of defending himself against the living germs.

PNEUMONIA.

W. N. GRACELY, M. D., HOME CITY, ()

Of all the severe acute, infectious diseases, lobar or croupous pneumonia is decidedly the most frequent and important. It is familiarly known to the laity as lung fever. In many cases the disease is primary and may occur suddenly in persons of fairly good health.

Pneumonia can be looked for as a complication in other diseased conditions, noticeably: typhoid, rheumatism or in surgical cases requiring extensive operative work. The disease is induced by the diplococcus lanceolatus and many of the symptoms are those of a septicaemia. Usually the subjective and objective symptoms produced are the most striking of the clinical phenomena, and in this feature pneumonia differs widely from other infectious fevers in which the general symtoms are more noticeable than the local infection.

The most striking feature of penumonia is its sudden onset. The majority of cases date their beginning from a pronounced rigor which may come at any time of the day or night and possibly with or

without exposure to extreme climatic conditions. The first subjective symptom after the chill, is a sharp stabbing pain in the side, especially on deep inspiration or while talking, and then respiration becomes faster, more superficial and often irregular in rhythm. This stitch in the side is very likely due to a ry pleurisy which follows the lung infection. With the characteristic pain, cough and fever follow in short order. The cough is very likely due to bronchitis which complicates the trouble in the alveoli.

With the cough we have a pecular viscid expectoration. Many men like to diagnose pneumonia from the rusty, prune juice or red color of the expectorate, which usually sticks to the vessel when inverted. In some cases cough and expectoration are slight, due to absorption of a great deal of the exudate without much liquification taking place. This expectoration may come on the first or second day, though frequently later. The fever is a prominent symptom and is of quick onset and rapid development; during or shortly after the initial chill we find the temperature rising. The height to which the fever goes is not a constant and fast point. Classically 104-105, it may never go beyond 101-103, even in severe cases. Hyperpyrexia may be followed by a favorable crisis especially when this occurs. within a few days after the onset. The pulse at first hard and quick speedily becomes small and rapid. Any irregularity is cause for watchfulness.

Physical examination reveals guiding symptoms. Inspection of the chest shows quick breathing with inspiration and expiration closely following each other, a long pause filling up the cycle. Acceleration is striking, 30-40 being usual and 50-60 to the minute are seen in cases which recover. The alae nasi dilate on inspiration and the muscles of the neck contract with visible effort. Auscultation reveals more than percussion; the crepitant rales of the first stages are replaced by bronchial breathing with its loud sound close to the ear. With complete infiltration of a lobe the bronchial murmur is heard with some moist rales. When resolution sets in the moist rales become prominent. The tongue is dry, coated and often typhoid like. Anorexia is customary. The bowels are constipated though diarrhea may be seen and may be troublesome. The jaundice seen with pneumonia is likely due to inflammation of the duodenum, though venous stasis may cause pressure on the bile ducts.

On testing the urine we find a deficiency of chlorides, due very likely to the exudate in the lungs. Some albumin is seen though symptons of nephritis usually disappear with the crisis if there has been sev re kidney trouble before. The urine, scanty, because of