The arteria vertebrails was ocluded by ligature on the left side of a heifer of the Spanish bullfightinhg breed between the VI and the VII cervical vertebrale, to produce an experimental sichaemia of the spinal cord. Another heifer was operated on in the same way on both sides. An experimental bullfight was held during 20 minutes. No collapse of the animals was observed. So it seems that the occlusion of the lateral spinal arteries by thrombosis or the inexistence of such arteries should be a necesary but insufficient  factor. The ischemic component coming from an emotional constriction of the arteries would be the most important one.

To try to prove this hypotesis an experiment was carried out giving an intramuscular injection of papaverine chlordidrate (0.3 g) 2 hours before starting the bullfight. The x2 test  of differences between treated and untreated groups gave a value of 6.6234, wich is statisfically significant at the 5 p. 100 level (adjusted value of x2 4.4817)