Figure 4. A P22 rat tumour (4 mm diameter) growing in a dorsal skin flap "window" chamber surgically implanted into a BDIX rat before and 3 h after treatment with 10 mg kg^–1 CA-4-P. Blood vessels are visualized by intravital microscopy under transmitted light using low power (upper panels) and high power (lower panels). After 3 h, when tumour blood flow is severely reduced (see Figures 2 and 3), blood vessels are clearly distended and there is significant haemorrhage especially around the tumour periphery.