_Circulatory System._—The pulse is rapid and feeble in the stage of evacuation to become imperceptible in the algid stage. The circulation is practically at a standstill so that only a few drops of black tarry blood, which does not coagulate readily, flow from a wound of a vein when giving an intravenous injection. The blood is concentrated and has a specific gravity of 1072 to 1078. The systolic pressure falls greatly, even to 60 mm. of mercury in a severe, or 75 mm. in a less serious case. The red cell count is increased to 7 or 8 million red cells per c.mm. and the leucocyte count reaches 15,000 to 50,000. _Nervous System._—The mind is clear, even when the patient seems profoundly apathetic. The muscle cramps are characteristic of the disease. DIAGNOSIS =Clinical Diagnosis.=—It is customary to state that cholera nostras and infections with virulent meat poisoning bacteria of the paratyphoid group show bile in the intestinal discharges and not the typical rice-water stools of true cholera. It must be remembered that these affections can at times show as marked muscular cramps, emaciation, cyanosis and weak voice as cholera so that only the bacteriological examination can differentiate. Algid pernicious malaria generally shows a rather high axillary temperature and the stools are rarely so profuse as in cholera. In ptomaine or mushroom poisoning the vomiting usually precedes the diarrhoea—the opposite of the order in cholera. Acute intestinal obstructions may simulate but here we have faecal vomiting and constipation. With irritant poisons as arsenic or antimony there is the metallic taste and the pains are chiefly colicky rather than muscular and the stools rather dysenteric. I have seen severe cases of bacillary dysentery which could not be differentiated clinically from cholera, and it is interesting to note that many cases of cholera occurring in the Balkan war were diagnosed as bacillary dysentery. In children cerebral manifestations are very common so that in the Philippines many such cholera cases were diagnosed as meningitis. =Laboratory Diagnosis.=—Agglutination is the practical aid in diagnosis. The serum from cholera convalescents, or those vaccinated against cholera, show agglutinins. It has been stated that properly vaccinated cases show a titre of from 1 to 2 thousand in about 70% of cases. Normal human serum does not agglutinate in a higher dilution than 1 to 20. Greig has found that fatal cholera cases rarely give higher than 1 to 40. In cases recovering he found well-marked agglutinating power by the 6th day, titres of 1 to 500 or 1 to 1000 being frequently obtained. Janoue and Watanabe found the agglutinating power of the sera of convalescents to fall rapidly after the third week. As a rule the titre varied from 1 to 100 to 1 to 400. The highest titre noted was 1 to 10,000.