As a rule, a sharp fall in the leucocytic curve occurs within 1 or 2 minutes after the meal; generally the curve rises within 10 to 20 minutes, but often a second fall follows 30 to 50 minutes after the meal. This may be followed by a slow rise in the curve (physiological leucocytosis). The first sharp fall is often accompanied by a similar decrease in red cells, the leucocytic formula is not changed, the blood pressure also remains unchanged, and this makes it probable that the leucopenia observed is only a manifestation of a change in distribution of the blood in different regions of the body.

Not infrequently the leucocyte curve after ingestion of food shows a form differing considerably from that described above. Counts of white cells made at intervals of 20 minutes in the same patient at different times but after ingestion of the same food show very different leucocytic curves. Such counts do not give evidence of the existence of a crise hémoclasique and consequently cannot be used to identify the causative agent of cases of hypersensitiveness to foodstuffs or drugs. Whether such an identification can be obtained if instead of simply counting white cells the whole complex of symptoms originally described by Widal as characteristic for a crise hémoclasique is used, remains undetermined by our work.