It is important the the phenol in almond oil does not spray into the surgeon's eyes when he is injecting the patient, so there should be a luer lock to connect the needle to the syringe. The luer lock prevents separation of the syringe from the needle.
The syringe has three loops on it, so the surgeon can aspirate and inject with one hand, (the surgeon uses his other hand to hold the proctoscope steady). The thumb is inserted through the large ring at the end of the plunger and the index and middle fingers through the two rings attached to the barrell.
The needle has an angle on it to facilitate entry into the submucosa. If there was no angle the surgeon would be more likely to inject too deeply. The surgon introduces the needle into the anal canal through the proctoscope with the concavity of the bend pointing into the middle of the anal canal.