“What do you call a can opener that won’t work? A can’t opener.”

Greg Morton is, by his own description, “not a particularly funny man,” and yet he ekes out a living — specifically, eking out his rent at the Plaza Hotel downtown — as best he can, by telling jokes. He will accept donations for either clean gags or more, say, blue material as he sits in his manually powered wheelchair beneath a rectangular canopy that reads “Self Employed.” Beneath that, “MS” and then, “I Tell Jokes.”

The MS refers to Morton’s condition of multiple sclerosis, a degenerative disease of the myelin, or sheathing, around pathways to the brain or spinal cord that become inflamed and swollen. The cause for this condition is unknown and no cure is on any visible horizon according to a search on MSLifelines.com, a website devoted to the disease. The disorder characteristically manifests (most commonly in women) between the ages of 20 and 40. Morton, now 43, was diagnosed some seven months ago. Blurred vision and slurred speech are also characteristic among a wide variety of the disease’s manifestations, and Morton experiences these symptoms among others. Another common phenomenon with MS is remission and relapse — multiple relapses and sometimes very long periods of symptom-free remission that can last for 20 to 30 years. Morton enjoys no such luxury.

Morton is smiley, clean-cut, and boyish. His main concern is making his rent ($140 per week for minimal accommodations) as well as being perceived as someone not seeking a “free ride.”

“My arthritis has always been in my hands, but I’ve worked. I drove a taxi in Dallas for years. I’m from Dallas...did I say that?” Morton has a round, moonish face. From the top of his head sprout several inches of straight, wheat-colored brush; and his smile, punctuated regularly by a downward bow and almost somber-toned commentary, reveals a flash of either missing or somehow foreshortened teeth. “I drove a cab for about 20 years. I could do that because I didn’t have to grip anything; I could just work the steering wheel with my palms.” He demonstrates with short, almost gnarled and thick fingers in workout gloves with the fingers cut away. “Joke?” He asks a passerby who has stopped to read his sign.

“MS. Master slayer, eh?” the stranger says to no one in particular. “Yeah, I’ll take a joke.” This to Morton.

“Clean or dirty?” The gloved man spreads his palms.

“Clean.”

“What do you call a cow that has just given birth?”

“Moooom?”

“No. Decaffeinated.”

“Hah! Okay.” The man produces a dollar and then rounds C Street at Fifth Avenue. Morton’s rolling grounds are in front of the 7-Eleven or Rite Aid on the next block and over to Broadway, roughly between Fourth and Sixth, about the same on C. The trolley cops have no problem with Greg Morton, as he is neither panhandling nor blocking traffic. Morton is proud of the fact that his canopy does not protrude beyond the tracks of his wheels on either side. “My space signature is the same as a standing person.” He remains to one side of flowing foot traffic.

Another customer with a young girlfriend of maybe 16 stops. The young man presents two dollars. “Keep it clean, now.”

“Okay. You know why anteaters never get sick?”

“Uh-uh. No.”

“Because they’re full of antibodies,” pronouncing it “anteee-bodies.” Turning to me again, he says, “See, I told you I’m not that funny.” Looking up and down the street, he says, “If people really want to help me, I don’t need money for anything like drugs or anything. I just really worry about rent. If they want, people could just leave a few dollars at the desk at the hotel for me at 1037 Fourth, in number 412, the Joke Teller. I need another $40 between now and Sunday. That’s what I need. That’s what I worry about. Hey, wanna see something? Put your fingertips right here. I’ve got a hole in my chest.”

Morton takes hold of my karate-poised fingertips and places them against his rib cage — or where his ribs should be — just to his left side, just where they tell you your heart is, though it isn’t, really. Morton has a cavity where his ribs should have closed to form a cage. “Another birth defect,” he says. “My ribs don’t meet there. No bone. Only this layer of skin separates my heart from here,” he gestures with his palm at the air directly in front of his torso.

It is difficult to know what to say. I don’t recall ever encountering such vulnerability beyond the softness of a newborn’s scalp. I say nothing.